DISULFIDE BOND MAPPING OF PROTEINS BY CYANYLATION

对蛋白质结构的了解需要确定哪一个 半胱氨酸与哪种半胱氨酸相连。我们变本加厉，割裂 游离半胱氨酸残基N-末端的多肽键。从 已知的序列，我们可以预测降解肽的质量 给出了二硫键连接性。我们目前使用的是 氰基二氨基吡啶(CDAP)四氟硼酸盐，它使氰基 在pH值为3的蛋白质，以避免二硫键交换。我们已经确立了 低pH条件下部分还原的条件，也避免了二硫化物 债券交易所。我们对核糖核酸酶A使用了这种方法，它 给出了四个单一还原的异构体，每个都有不同的二硫键 债券减少。这些异构体被氰化和裂解以供分析 通过MALDI-MS，我们可以验证二硫键的配对。 我们还在探索交替氰化的适用性。 为我们在化学方法中提供一些灵活性的试剂 来解决一个结构性问题。我们合成了一种新试剂， 2-硫氰基吡啶，将表征其在 氰化模型化合物，如β-乳球蛋白等。

A knowledge of protein structure requires a determination of which cysteine is connected to which cysteine. We cyanylate and cleave the peptide bond at the N-terminus of free cysteine residues. From the known sequence, we can anticipate the mass of degraded peptides for a given disulfide bond connectivity. We presently use cyanodiaminopyridium (CDAP) tetrafluoroborate, which cyanylates the protein at pH 3 to avoid disulfide bond exchange. We have established conditions for partial reduction at low pH which also avoids disulfide bond exchange. We have used this approach with ribonuclease A, which gives four singly reduced isomers, each having a different disulfide bond reduced. These isoforms were cyanylated and cleaved for analysis by MALDI-MS allowing us to verify the pairing of the disulfide bonds. We are also exploring the applicability of alternate cyanylating reagents to provide us with some flexibility in the chemical approach to solving a structural problem. We have synthesized a new reagent, 2-thiocyanopyridine, which will be characterized for its potency in cyanylating model compounds such as ?-lactoglobulin and others.