Dr. Manicam is supported by the Internal University Research Funding (Stufe 1) from the University Medical Centre of the Johannes Gutenberg University Mainz and a grant from the Deutsche Forschungsgemeinschaft (MA 8006/1-1).

<ol>
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R., Ge, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Top-down+proteomics+in+health+and+disease:+Challenges+and+opportunities.">Top-down proteomics in health and disease: Challenges and opportunities.</a> Proteomics. 14, 1195-1210 (2014).</li><li>Aebersold, R., Mann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry-based+proteomics.">Mass spectrometry-based proteomics.</a> Nature. 422, 198-207 (2003).</li><li>Aebersold, R., Mann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass-spectrometric+exploration+of+proteome+structure+and+function.">Mass-spectrometric exploration of proteome structure and function.</a> Nature. 537, 347-355 (2016).</li><li>Cehofski, L. J., Mandal, N., Honor&#233;, B., Vorum, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+platforms+in+vitreoretinal+proteomics.">Analytical platforms in vitreoretinal proteomics.</a> Bioanalysis. 6, 3051-3066 (2014).</li><li>Manicam, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomics+Unravels+the+Regulatory+Mechanisms+in+Human+Tears+Following+Acute+Renouncement+of+Contact+Lens+Use:+A+Comparison+between+Hard+and+Soft+Lenses.">Proteomics Unravels the Regulatory Mechanisms in Human Tears Following Acute Renouncement of Contact Lens Use: A Comparison between Hard and Soft Lenses.</a> Scientific Reports. 8, 11526 (2018).</li><li>Perumal, N., Funke, S., Pfeiffer, N., Grus, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+lacrimal+proline-rich+protein+4+(PRR+4)+in+human+tear+proteome.">Characterization of lacrimal proline-rich protein 4 (PRR 4) in human tear proteome.</a> Proteomics. 14, 1698-1709 (2014).</li><li>Perumal, N., Funke, S., Pfeiffer, N., Grus, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomics+analysis+of+human+tears+from+aqueous-deficient+and+evaporative+dry+eye+patients.">Proteomics analysis of human tears from aqueous-deficient and evaporative dry eye patients.</a> Scientific Reports. 6, 29629 (2016).</li><li>Perumal, N., Funke, S., Wolters, D., Pfeiffer, N., Grus, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+human+reflex+tear+proteome+reveals+high+expression+of+lacrimal+proline-rich+protein+4+(PRR4).">Characterization of human reflex tear proteome reveals high expression of lacrimal proline-rich protein 4 (PRR4).</a> Proteomics. 15, 3370-3381 (2015).</li><li>Perumal, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+human+aqueous+humour+proteome:+A+comparison+of+the+genders.">Characterization of the human aqueous humour proteome: A comparison of the genders.</a> PloS ONE. 12, 0172481 (2017).</li><li>Hayreh, S. 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The authors have nothing to disclose.

Comprehensive proteome profiling of a diverse range of ocular samples is an important and indispensable first step to elucidate the molecular mechanisms and signaling pathways implicated in health and disease. In order to obtain high quality data and to ensure the reproducibility of results obtained from these analyses, the preceding sample preparation steps are crucial, as highlighted in a review by Mandal et al. that discussed in-depth the sample processing procedures for different parts of the eye employing two-dimens...

The advancement in the field of proteomics, which permits integrated and unsurpassed data collection power, has greatly revolutionized our understanding of the molecular mechanisms underlying certain disease conditions as well as in reflecting the physiological state of a specific cell population or tissue1,2,3,4. Proteomics has also proved to be an important platform in ophthalmic research owing to the sensitivity and unbiased analysis of different ocular samples that facilitated identification of potential disease markers for eventual diagnosis and prognosis, as evidenced elegantly by many studies in recent years, including some of ours1,5,6,7,8,9,10. However, it is often difficult to obtain human samples for proteomic analyses due to ethical reasons, especially considering the need for control material from healthy individuals for reliable comparative analyses. On the other hand, it is also challenging to obtain sufficient amount of samples for optimal and reliable mass spectrometric analyses. This is particularly crucial for mass-limited biological materials such as the micro-blood vessels of the eye. One such major retrobulbar blood vessel that plays pivotal roles in the regulation of ocular blood flow is the short posterior ciliary artery (sPCA). Any perturbation or anomalies in this vascular bed may result in severe clinical repercussions, which can lead to the pathogenesis of several sight-threatening diseases such as glaucoma and nonarteritic anterior ischemic optic neuropathy (NAION)11,12. However, there is a lack of studies elucidating the proteome changes in this arterial bed due to the above-mentioned drawbacks. Therefore, in recent years, the house swine (Sus scrofa domestica Linnaeus, 1758) has emerged as a good animal model in ophthalmic research owing to the high morphologic and phylogenetic similarities between humans and pigs13,14,15. Porcine ocular samples are easily available and most importantly, are more accurate representation of human tissues.
Considering the important role of these blood vessels in the eye, as well as the dearth of methodology catered for efficient protein extraction and analyses from these microvessels, we have previously characterized the proteome of the porcine sPCA using an in-house protocol that resulted in the identification of a high number of proteins16. Based on this study, we have further optimized and described in-depth our methodology in this article, which allows proteome analysis from minute amounts of samples using the porcine sPCA as model tissue. Albeit the main aim of this study was to establish a MS-compatible methodology for mass-limited ocular blood vessels, we have provided substantial experimental evidence that the described workflow can also be broadly applied to various tissue-based samples.
It is envisioned that this workflow will be instrumental for preparation of high-quality MS-compatible samples from small quantities of materials for comprehensive proteome analyses.

<table border="0" cellpadding="0" cellspacing="0" style="width:1040px;" width="1039">
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	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:436px;">A. Chemicals</td>
			<td style="width:281px;"></td>
			<td style="width:120px;"></td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1, 4-Dithiothreitol (DTT)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:120px;">1.11474</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium bicarbonate (ABC, CH&#8325;NO&#8323;)</td>
			<td>Sigma-Aldrich</td>
			<td>5.33005</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Calcium chloride dihydrate (CaCl2)&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>5239.1</td>
			<td>2.5 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#39;s phosphate-buffered saline (PBS)&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific</td>
			<td>14190169</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Formic acid (CH2O2)</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A0748</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">HPLC-grade acetonitrile (ACN, C2H3N)</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A1605</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">HPLC-grade methanol (CH3OH)</td>
			<td style="width:281px;">Fisher Scientific</td>
			<td style="width:120px;">M/4056/17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HPLC-grade water&#160;</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A1589</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iodoacetamide (IAA)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:120px;">I6125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Kalium chloride (KCl)&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>6781.1</td>
			<td>4.7 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Kalium dihydrogen phosphate (KH2PO4)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>3904.2</td>
			<td>1.2 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS-grade acetic acid</td>
			<td style="width:281px;">&#160;Carl Roth&#160;</td>
			<td style="width:120px;">AE69.1</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Magnesium sulphate (MgSO4)&#160;&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td style="width:120px;">261.2</td>
			<td>1.2 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE Antioxidant</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">NP0005</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE LDS Sample buffer&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0007</td>
			<td>4x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE MES SDS Running Buffer&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0002</td>
			<td>20x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE Sample reducing agent&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0004</td>
			<td>10x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SeeBlue Plus2 pre-stained protein standard&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">LC5925</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sequencing grade modified trypsin</td>
			<td style="width:281px;">Promega</td>
			<td style="width:120px;">V5111</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium chloride (NaCl)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>9265.2</td>
			<td>118.3 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Sodium hydrogen carbonate (NaHCO3)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>965.3</td>
			<td>25 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Trifluoroacetic acid (TFA,&#160; C2HF3O2)</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">108178</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#945;-(D)-(+)- Glucose monohydrate</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>6780.1</td>
			<td>11 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">B. Reagents and Kits</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.5mm zirconium oxide beads&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">ZROB05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1.0mm zirconium oxide beads&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">ZROB10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Colloidal Blue Staining&#160; Kit</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">LC6025</td>
			<td>To stain 25 mini gels per kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE 4-12 % Bis-Tri gels</td>
			<td>Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0321BOX</td>
			<td>1.0 mm, 10-well</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pierce Bicinchoninic Acid (BCA) Protein Assay Kit&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific</td>
			<td style="width:120px;">23227</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ProteoExtract Transmembrane Protein Extraction Kit, TM-PEK</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">71772-3</td>
			<td>20 reactions per kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tissue Protein Extraction Reagent (T-PER)</td>
			<td style="width:281px;">Thermo Scientific</td>
			<td style="width:120px;">78510</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">C. Tools</td>
			<td style="width:281px;"></td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">96-well V-bottom plates</td>
			<td style="width:281px;">Greiner Bio-One</td>
			<td style="width:120px;">651180</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Corning 96-well flat-bottom plates</td>
			<td style="width:281px;">Sigma-Aldrich</td>
			<td style="width:120px;">CLS3595-50EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Disposable microtome blades</td>
			<td>pfm Medical</td>
			<td>207500014</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Disposable scalpels #21</td>
			<td>pfm Medical</td>
			<td>200130021</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dissection pins&#160;</td>
			<td style="width:281px;">Carl Roth</td>
			<td style="width:120px;">PK47.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Extra Fine Bonn Scissors</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td style="width:120px;">14084-08</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Falcon conical centrifuge tubes (50 mL)</td>
			<td>Fisher Scientific</td>
			<td>14-432-22</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mayo scissors, Tough cut</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td style="width:120px;">14130-17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Precision tweezers</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td>11251-10</td>
			<td>Type 5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Precision tweezers, straight with extra fine tips</td>
			<td style="width:281px;">Carl Roth</td>
			<td>LH53.1</td>
			<td>Type 5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Self-adhesive sealing films for microplates</td>
			<td style="width:281px;">Ratiolab (vWR)</td>
			<td style="width:120px;">RATI6018412</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Standard pattern forceps</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
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		<tr height="21">
			<td height="21" style="height:21px;">Student Vannas spring scissors</td>
			<td>&#160;Fine Science Tools</td>
			<td>91501-09</td>
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		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vannas capsulotomy scissors&#160;&#160;</td>
			<td style="width:281px;">Geuder</td>
			<td style="width:120px;">19760</td>
			<td>&#160;Straight, 77 mm</td>
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			<td height="25" style="height:25px;">ZipTipC18 pipette tips</td>
			<td style="width:281px;">Merck Millipore</td>
			<td>ZTC18S096</td>
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		<tr height="21">
			<td height="21" style="height:21px;">150 &#215; 0.5 mm BioBasic C18 column</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">72105-150565</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">30 &#215; 0.5 mm BioBasic C18 pre-column&#160;</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">72105-030515</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Amicon Ultra-0.5 3K Centrifugal Filter Devices&#160;</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">UFC500396</td>
			<td>Pack of 96.</td>
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		<tr height="21">
			<td height="21" style="height:21px;">Analytical balance</td>
			<td>Sartorius</td>
			<td>H51</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;">Autosampler&#160;</td>
			<td>CTC Analytics AG, Zwingen, Switzerland</td>
			<td style="width:120px;">HTS Pal</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BBY24M Bullet Blender Storm&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">NA-BB-25</td>
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			<td height="21" style="height:21px;">Eppendorf concentrator, model 5301</td>
			<td style="width:281px;">Sigma-Aldrich</td>
			<td style="width:120px;">Z368172</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Eppendorf microcentrifuge, model 5424</td>
			<td style="width:281px;">Fisher Scientific</td>
			<td style="width:120px;">05-403-93</td>
			<td>Non-refrigerated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heraeus Primo R Centrifuge</td>
			<td style="width:281px;">Thermo Scientific</td>
			<td style="width:120px;">75005440</td>
			<td>Refrigerated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Labsonic M Ultrasonic homogenizer&#160;</td>
			<td style="width:281px;">Sartorius</td>
			<td style="width:120px;">BBI-8535027</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS pump, model Rheos Allegro</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">22080</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LTQ Orbitrap XL mass spectrometer&#160;</td>
			<td>Thermo Scientific, Bremen, Germany</td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Multiskan Ascent plate reader&#160;</td>
			<td style="width:281px;">Thermo Labsystems</td>
			<td style="width:120px;">v2.6</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rotator with vortex&#160;</td>
			<td style="width:281px;">neoLab</td>
			<td style="width:120px;">7-0045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium probe (&#216; 0.5mm, 80mm long)</td>
			<td style="width:281px;">Sartorius</td>
			<td style="width:120px;">BBI-8535612</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic bath, type RK 31</td>
			<td style="width:281px;">Bandelin</td>
			<td style="width:120px;">329</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Xcell Surelock Mini Cell</td>
			<td>Life Technologies</td>
			<td>El0001</td>
			<td></td>
		</tr>
	</tbody>
</table>

sample preparation for mass-spectrometry-based proteomics analysis of ocular microvessels

The use of isolated ocular blood vessels in vitro to decipher the pathophysiological state of the eye using advanced technological approaches has greatly expanded our understanding of certain diseases. Mass spectrometry (MS)-based proteomics has emerged as a powerful tool to unravel alterations in the molecular mechanisms and protein signaling pathways in the vascular beds in health and disease. However, sample preparation steps prior to MS analyses are crucial to obtain reproducible results and in-depth elucidation of the complex proteome. This is particularly important for preparation of ocular microvessels, where the amount of sample available for analyses is often limited and thus, poses a challenge for optimum protein extraction. This article endeavors to provide an efficient, rapid and robust protocol for sample preparation from an exemplary retrobulbar ocular vascular bed employing the porcine short posterior ciliary arteries. The present method focuses on protein extraction procedures from both the supernatant and pellet of the sample following homogenization, sample cleaning with centrifugal filter devices prior to one-dimensional gel electrophoresis and peptide purification steps for label-free quantification in a liquid chromatography-electrospray ionization-linear ion trap-Orbitrap MS system. Although this method has been developed specifically for proteomics analyses of ocular microvessels, we have also provided convincing evidence that it can also be readily employed for other tissue-based samples.

Limited sample availability is one of the major drawbacks in ophthalmic research. Correspondingly, extraction methods for optimum protein yield from small amounts of samples such as ocular blood vessels are often debatable. To date, there is a paucity of methods catered particularly for protein extraction from retrobulbar blood vessels. Therefore, as a first step in method optimization and as a proof-of-principle to compare the efficacy and robustness of several commonly employed protein ...

Watch this Scientific Journal Video about Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels at JoVE.com

Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels

Proteome characterization of ocular microvascular beds is pivotal for in-depth understanding of many ocular pathologies in humans. This study demonstrates an effective, rapid, and robust method for protein extraction and sample preparation from small blood vessels employing the porcine short posterior ciliary arteries as model vessels for mass-spectrometry-based proteomics analyses.

The use of isolated ocular blood vessels in vitro to decipher the pathophysiological state of the eye using advanced technological approaches has greatly ...

sample-preparation-for-mass-spectrometry-based-proteomics-analysis

Universidad de Cartagena UDEC

Research

JoVE Journal

Biology

11.2K Views.  University Medical Centre of the Johannes Gutenberg University Mainz. Proteome characterization of ocular microvascular beds is pivotal for in-depth understanding of many ocular pathologies in humans. This study demonstrates an effective, rapid, and robust method for protein extraction and sample preparation from small blood vessels employing the porcine short posterior ciliary arteries as model vessels for mass-spectrometry-based proteomics analyses.

Video: Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels

Western Blotting: Sample Preparation to Detection

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native or denatured proteins by the length of the polypeptide (denaturing conditions) or by the 3-D structure of the protein (native/ non-denaturing conditions). The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are probed (detected) using antibodies specific to the target protein.

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract.

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract. It uses gel ...

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling processes. Extracting sterol-enriched membrane microdomains from plant cells for proteomic analysis is a difficult task mainly due to multiple preparation steps and sources for contaminations from other cellular compartments. The plasma membrane constitutes only about 5-20% of all the membranes in a plant cell, and therefore isolation of highly purified plasma membrane fraction is challenging. A frequently used method involves aqueous two-phase partitioning in polyethylene glycol and dextran, which yields plasma membrane vesicles with a purity of 95% 1. Sterol-rich membrane microdomains within the plasma membrane are insoluble upon treatment with cold nonionic detergents at alkaline pH. This detergent-resistant membrane fraction can be separated from the bulk plasma membrane by ultracentrifugation in a sucrose gradient 2. Subsequently, proteins can be extracted from the low density band of the sucrose gradient by methanol/chloroform precipitation. Extracted protein will then be trypsin digested, desalted and finally analyzed by LC-MS/MS. Our extraction protocol for sterol-rich microdomains is optimized for the preparation of clean detergent-resistant membrane fractions from Arabidopsis thaliana cell cultures.
We use full metabolic labeling of Arabidopsis thaliana suspension cell cultures with K15NO3 as the only nitrogen source for quantitative comparative proteomic studies following biological treatment of interest 3. By mixing equal ratios of labeled and unlabeled cell cultures for joint protein extraction the influence of preparation steps on final quantitative result is kept at a minimum. Also loss of material during extraction will affect both control and treatment samples in the same way, and therefore the ratio of light and heave peptide will remain constant. In the proposed method either labeled or unlabeled cell culture undergoes a biological treatment, while the other serves as control 4.

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Here we describe a robust method for the fractionation of plant plasma membranes into detergent resistant and detergent soluble membranes based on a mixture of unlabeled and in vivo fully 15N labeled Arabidopsis thaliana cell cultures. The procedure is applied for comparative proteomic studies to understand signaling processes.

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling ...

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale quantitative analysis of formalin fixed and paraffin embedded (FFPE) tissue. The procedure comprises four distinct steps. The first one is the preparation of sections from the FFPE material and microdissection of cells of interest. In the second step the isolated cells are lysed and processed using 'filter aided sample preparation' (FASP) technique. In this step, proteins are depleted from reagents used for the sample lysis and are digested in two-steps using endoproteinase LysC and trypsin. 
After each digestion, the peptides are collected in separate fractions and their content is determined using a highly sensitive fluorescence measurement. Finally, the peptides are fractionated on 'pipette-tip' microcolumns. The LysC-peptides are separated into 4 fractions whereas the tryptic peptides are separated into 2 fractions. In this way prepared samples allow analysis of proteomes from minute amounts of material to a depth of 10,000 proteins. Thus, the described workflow is a powerful technique for studying diseases in a system-wide-fashion as well as for identification of potential biomarkers and drug targets.

Archival formalin fixed and paraffin embedded (FFPE) clinical samples are valuable material for investigation of diseases. Here we demonstrate a sample preparation workflow allowing in-depth proteomic analysis of microdissected FFPE tissue.

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale ...

Enrichment of Extracellular Matrix Proteins from Tissues and Digestion into Peptides for Mass Spectrometry Analysis

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of cell proliferation, survival, migration, etc. The ECM plays important roles in development and in diverse pathologies including cardio-vascular and musculo-skeletal diseases, fibrosis, and cancer. Thus, characterizing the composition of ECMs of normal and diseased tissues could lead to the identification of novel prognostic and diagnostic biomarkers and potential novel therapeutic targets. However, the very nature of ECM proteins (large in size, cross-linked and covalently bound, heavily glycosylated) has rendered biochemical analyses of ECMs challenging. To overcome this challenge, we developed a method to enrich ECMs from fresh or frozen tissues and tumors that takes advantage of the insolubility of ECM proteins. We describe here in detail the decellularization procedure that consists of sequential incubations in buffers of different pH and salt and detergent concentrations and that results in 1) the extraction of intracellular (cytosolic, nuclear, membrane and cytoskeletal) proteins and 2) the enrichment of ECM proteins. We then describe how to deglycosylate and digest ECM-enriched protein preparations into peptides for subsequent analysis by mass spectrometry.

This protocol describes a procedure for enriching ECM proteins from tissues or tumors and deglycosylating and digesting the ECM-enriched preparations into peptides to analyze their protein composition by mass spectrometry.

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of ...

Sample Preparation for Mass Cytometry Analysis

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities for deep analysis well beyond what is possible with conventional fluorescence-based flow cytometry. As with any new technology, there are critical steps that help ensure the reliable generation of high-quality data. Presented here is an optimized protocol that incorporates multiple techniques for the processing of cell samples for mass cytometry analysis. The methods described here will help the user avoid common pitfalls and achieve consistent results by minimizing variability, which can lead to inaccurate data. To inform experimental design, the rationale behind optional or alternative steps in the protocol and their efficacy in uncovering new findings in the biology of the system being investigated is covered. Lastly, representative data is presented to illustrate expected results from the techniques presented here.

This article describes the collection and processing of samples for mass cytometry analysis.

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities ...

An Alternative Approach for Sample Preparation with Low Cell Number for TEM Analysis

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, especially cells in suspension such as hematopoietic stem cells (HSCs), remains limited due to the requirement of a high cell number during sample preparation. There are a few cytospin or monolayer approaches for TEM analysis from scarce samples, but these approaches fail to get significant quantitative data from the limited number of cells. Here, an alternative and novel approach for sample preparation in TEM studies is described for rare cell populations that enables quantitative analysis.
A relatively low cell number, i.e., 10,000 HSCs, was successfully used for TEM analysis compared to the millions of cells typically used for TEM studies. In particular, Evans blue staining was performed after paraformaldehyde-glutaraldehyde (PFA-GA) fixation to visualize the tiny cell pellet, which facilitated embedding in agarose. Clusters of numerous cells were observed in ultra-thin sections. The cells had a well preserved morphology, and the ultra-structural details of the Golgi complex and several mitochondria were visible. This efficient, easy and reproducible protocol allows sample preparation from a low cell number and can be used for qualitative and quantitative TEM analysis on rare cell populations from limited biological samples.

Here, we present a protocol to prepare samples with low cell numbers for transmission electron microscopy (TEM) analysis.

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, ...

Sample Preparation and Imaging of Exosomes by Transmission Electron Microscopy

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The contents and morphology of the secreted vesicles reflect cell behavior or physiological status, for example cell growth, migration, cleavage, and death. The exosomes&#39; role may depend highly on size, and the size of exosomes varies from 30 to 300 nm. The most widely used method for exosome imaging is negative staining, while other results are based on Cryo-Transmission Electron Microscopy, Scanning Electron Microscopy, and Atomic Force Microscopy. The typical exosome&#39;s morphology assessed through negative staining is a cup-shape, but further details are not yet clear. An exosome well-characterized through structural study is necessary particular in medical and pharmaceutical fields. Therefore, function-dependent morphology should be verified by electron microscopy techniques such as labeling a specific protein in the detailed structure of exosome. To observe detailed structure, ultrathin sectioned images and negative stained images of exosomes were compared. In this protocol, we suggest transmission electron microscopy for the imaging of exosomes including negative staining, whole mount immuno-staining, block preparation, thin section, and immuno-gold labelling.

This protocol describes the various techniques necessary for transmission electron microscopy including negative staining, ultrathin sectioning for detailed structure, and immuno-gold labelling to determine the positions of specific proteins in exosomes.

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The ...

Miniaturized Sample Preparation for Transmission Electron Microscopy

Due to recent technological progress, cryo-electron microscopy (cryo-EM) is rapidly becoming a standard method for the structural analysis of protein complexes to atomic resolution. However, protein isolation techniques and sample preparation methods for EM remain a bottleneck. A relatively small number (100,000 to a few million) of individual protein particles need to be imaged for the high-resolution analysis of proteins by the single particle EM approach, making miniaturized sample handling techniques and microfluidic principles feasible.
A miniaturized, paper-blotting-free EM grid preparation method for sample pre-conditioning, EM grid priming and post processing that only consumes nanoliter-volumes of sample is presented. The method uses a dispensing system with sub-nanoliter precision to control liquid uptake and EM grid priming, a platform to control the grid temperature thereby determining the relative humidity above the EM grid, and a pick-and-plunge-mechanism for sample vitrification. For cryo-EM, an EM grid is placed on the temperature-controlled stage and the sample is aspirated into a capillary. The capillary tip is positioned in proximity to the grid surface, the grid is loaded with the sample and excess is re-aspirated into the microcapillary. Subsequently, the sample film is stabilized and slightly thinned by controlled water evaporation regulated by the offset of the platform temperature relative to the dew-point. At a given point the pick-and-plunge mechanism is triggered, rapidly transferring the primed EM grid into liquid ethane for sample vitrification. Alternatively, sample-conditioning methods are available to prepare nanoliter-sized sample volumes for negative stain (NS) EM.
The methodologies greatly reduce sample consumption and avoid approaches potentially harmful to proteins, such as the filter paper blotting used in conventional methods. Furthermore, the minuscule amount of sample required allows novel experimental strategies, such as fast sample conditioning, combination with single-cell lysis for &#34;visual proteomics,&#34; or &#34;lossless&#34; total sample preparation for quantitative analysis of complex samples.

An instrument and methods for the preparation of nanoliter-sized sample volumes for transmission electron microscopy is presented. No paper-blotting steps are required, thus avoiding the detrimental consequences this can have for proteins, significantly reducing sample loss and enabling the analysis of single cell lysate for visual proteomics.

Due to recent technological progress, cryo-electron microscopy (cryo-EM) is rapidly becoming a standard method for the structural analysis of protein ...

Stomata Tape-Peel: An Improved Method for Guard Cell Sample Preparation

The study of guard cells is essential to the knowledge of the specific contributions of this cell type to the overall function of plants. However, it is often difficult to isolate and thus studying them often provides a challenge. 
This study establishes a stomatal guard cell enrichment method. The protocol utilizes Scotch tape to isolate guard cells and extract proteins from the cells. This method improves the integrity and yield of guard cell during isolation and provides a reliable sample for the study of cell signaling processes and how they correlate to stomatal movement phenotypes. In this method, the plant leaves were partitioned between two portions of tape and peeled apart to remove the abaxial side. This protocol was applied to Arabidopsis leaf tissue to isolate guard cells. The cells were treated with fluorescein diacetate (FDA) to determine viability and with abscisic acid (ABA) to assess stomata movement in response to ABA. In conclusion, this protocol proves useful for preparing enriched stomatal guard cells and isolating proteins. The quality of the cells and proteins obtained here enable physiological and other biological studies.

This protocol describes a method of preparing enriched stomatal guard cells that is useful for physiological and other biological studies.

The study of guard cells is essential to the knowledge of the specific contributions of this cell type to the overall function of plants. However, it is ...

Comprehensive Workflow of Mass Spectrometry-based Shotgun Proteomics of Tissue Samples

Recent advances in mass spectrometry have resulted in deep proteomic&#160;analysis along with the generation of&#160;robust and&#160;reproducible datasets. However, despite the considerable technical advancements, sample preparation from biospecimens such as patient blood, CSF, and tissue still poses considerable challenges. For identifying biomarkers, tissue proteomics often provides an attractive sample source to translate the research findings from the bench to the clinic. It can reveal potential candidate biomarkers for early diagnosis of cancer and neurodegenerative diseases such as Alzheimer&#39;s disease, Parkinson&#39;s disease, etc. Tissue proteomics also yields a wealth of systemic information based on the abundance of proteins and helps to address interesting biological questions.
Quantitative proteomics analysis can be grouped into two broad categories: a label-based and a label-free approach. In the label-based approach, proteins or peptides are labeled using stable isotopes such as SILAC (stable isotope labeling with amino acids in cell culture) or by chemical tags such as ICAT (isotope-coded affinity tags), TMT (tandem mass tag) or iTRAQ (isobaric tag for relative and absolute quantitation). Label-based approaches have the advantage of more accurate quantitation of proteins and using isobaric labels, multiple samples can be analyzed in a single experiment. The label-free approach provides a cost-effective alternative to label-based approaches. Hundreds of patient samples belonging to a particular cohort can be analyzed and compared with other cohorts based on clinical features. Here, we have described an optimized quantitative proteomics workflow for tissue samples using label-free and label-based proteome profiling methods, which is crucial for applications in life sciences, especially biomarker discovery-based projects.

The described protocol provides an optimized quantitative proteomics analysis of tissue samples using two approaches: label-based and label free quantitation. Label-based approaches have the advantage of more accurate quantitation of proteins, while a label-free approach is more cost-effective and used to analyze hundreds of samples of a cohort.

Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels

Summary

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Chapters in this video

Western Blotting: Sample Preparation to Detection

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

Enrichment of Extracellular Matrix Proteins from Tissues and Digestion into Peptides for Mass Spectrometry Analysis

Sample Preparation for Mass Cytometry Analysis

An Alternative Approach for Sample Preparation with Low Cell Number for TEM Analysis

Sample Preparation and Imaging of Exosomes by Transmission Electron Microscopy

Miniaturized Sample Preparation for Transmission Electron Microscopy

Stomata Tape-Peel: An Improved Method for Guard Cell Sample Preparation

Comprehensive Workflow of Mass Spectrometry-based Shotgun Proteomics of Tissue Samples