Tummala Rama, Green-Church Kari B, Limbach Patrick A
429K Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, P.O. Box 210172, 45221-0172, Cincinnati, OH, USA.
J Am Soc Mass Spectrom. 2005 Sep;16(9):1438-1446. doi: 10.1016/j.jasms.2005.04.006.
Although sodium dodecyl sulfate (SDS) is routinely used as a denaturing agent for proteins, its presence is highly detrimental on the analysis of peptides and proteins by mass spectrometry. It has been found, however, that when SDS is present in concentrations near to or above its critical micelle concentration (CMC), improvements in the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of peptide mixtures or hydrophobic proteins are obtained. To elucidate possible explanations for such improvements, here we have undertaken a study examining the effect of SDS micelles on peptide mixtures. Fluorescently labeled peptides were used as probes to determine whether hydrophobic or hydrophilic peptides interact exclusively with SDS micelles. In addition, four globular proteins were digested with trypsin and then various amounts of SDS were added before MALDI mass spectrometry. To examine the role of mixture complexity on the mass spectral results, the tryptic digest of bovine serum albumin was also fractionated according to hydrophobicity before SDS treatment. Results from these experiments suggest that micelle-peptide interactions increase peptide-matrix cocrystallization irrespective of analyte hydrophobicity. As these studies were performed using the dried-droplet method of sample spotting, the presence of micelles is also hypothesized to reduce Marangoni effects during the crystallization process.
尽管十二烷基硫酸钠（SDS）通常用作蛋白质的变性剂，但其存在对通过质谱分析肽和蛋白质极为不利。然而，已发现当SDS的浓度接近或高于其临界胶束浓度（CMC）时，肽混合物或疏水蛋白质的基质辅助激光解吸/电离质谱（MALDI-MS）分析会得到改善。为了阐明这种改善的可能原因，我们在此进行了一项研究，考察SDS胶束对肽混合物的影响。使用荧光标记的肽作为探针，以确定疏水或亲水肽是否仅与SDS胶束相互作用。此外，用胰蛋白酶消化四种球状蛋白质，然后在进行MALDI质谱分析之前加入不同量的SDS。为了考察混合物复杂性对质谱结果的作用，还在SDS处理之前根据疏水性对牛血清白蛋白的胰蛋白酶消化产物进行了分级分离。这些实验的结果表明，无论分析物的疏水性如何，胶束-肽相互作用都会增加肽-基质共结晶。由于这些研究是使用样品点样的干滴法进行的，因此还推测胶束的存在会减少结晶过程中的马兰戈尼效应。
