Kast Jürgen, Gentzel Marc, Wilm Matthias, Richardson Keith
The Biomedical Research Center, University of British Columbia, Vancouver, British Columbia, Canada.
J Am Soc Mass Spectrom. 2003 Jul;14(7):766-76. doi: 10.1016/S1044-0305(03)00264-2.
The sensitivity of protein identification by peptide sequencing using a nanoelectrospray ion source is limited by our ability to identify peptide ions in the mass spectrum. Their intensity must be higher than the chemical noise level to allow a rapid localization in the spectrum. Multiply-charged peptide ions on or below this level can only be found because their isotopic pattern is denser than that of the mostly singly-charged chemical background ions. However, to find peptides by looking for multiply-charged isotope clusters can be very timeconsuming and may lead to misassignments of the first isotope. Here we present a software-based method to increase the signal to noise ratio of ion signals in an electrospray spectrum. The software has two elements, one to reduce the noise level and a second to increase the intensity of ion peaks. Both methods together generate a spectrum in which the signal to noise ratio of ion signals is considerably improved. Peptide ions previously hidden in the chemical background are dismantled and can now be localized and selected for fragmentation. The method has been used successfully to identify low level proteins separated by one dimensional gel electrophoresis.
使用纳米电喷雾离子源通过肽测序鉴定蛋白质的灵敏度受到我们在质谱中鉴定肽离子能力的限制。它们的强度必须高于化学噪声水平，以便在光谱中快速定位。处于或低于此水平的多电荷肽离子只能被发现，因为它们的同位素模式比大多为单电荷的化学背景离子更密集。然而，通过寻找多电荷同位素簇来寻找肽可能非常耗时，并且可能导致对第一个同位素的错误归属。在这里，我们提出了一种基于软件的方法来提高电喷雾光谱中离子信号的信噪比。该软件有两个要素，一个是降低噪声水平，另一个是增加离子峰的强度。这两种方法共同生成一个光谱，其中离子信号的信噪比得到了显著提高。以前隐藏在化学背景中的肽离子被拆解，现在可以定位并选择进行碎片化。该方法已成功用于鉴定通过一维凝胶电泳分离的低丰度蛋白质。
