Barber-Armstrong Wendy, Donaldson Teraya, Wijesooriya Himali, Silva R A Gangani D, Decatur Sean M
Department of Chemistry, Mount Holyoke College, Carr Laboratory, S. Hadley, Massachusetts 01075, USA.
J Am Chem Soc. 2004 Mar 3;126(8):2339-45. doi: 10.1021/ja037863n.
Infrared spectroscopy (IR) is commonly used to study secondary structure of both peptides and proteins. The amide I band is very sensitive to peptide secondary structure, and the conformation of a peptide can be probed at the residue level by introducing site-specific isotope-labels into the peptide backbone. The replacement of a carbonyl (12)C with a (13)C results in a approximately 40 cm(-1) shift in the amide I' band. The amide I bands of specifically labeled helices should vary systematically as a function of the number and relative spacing of the labeled residues; thus one should be able to describe the conformation of a polypeptide in substantial detail by probing the changes in IR spectra as a function of the number and positioning of isotope labels. In this study, we report IR spectra of a series of differently labeled helical peptides. A series of 25mer peptides were synthesized based on the repeat sequence (AAAAK)(n). We have varied the number and spacing of the labels on each peptide and studied the changes in the (12)C and (13)C amide I' band due to label position. Our results indicate that changing the number of labels changes the frequency and intensity of both the (12)C and the (13)C amide mode. We also found that varying the spacing between labels causes these amide peaks to shift. Isotope labeling, combined with IR spectroscopy and theoretical predictions, may generate a description of peptide backbone conformations at the residue level.
红外光谱法（IR）常用于研究肽和蛋白质的二级结构。酰胺I带对肽的二级结构非常敏感，通过在肽主链中引入位点特异性同位素标记，可以在残基水平上探测肽的构象。用（13）C取代羰基（12）C会导致酰胺I'带发生约40 cm（-1）的位移。特异性标记螺旋的酰胺I带应根据标记残基的数量和相对间距系统地变化；因此，通过探测红外光谱随同位素标记数量和位置的变化，应该能够相当详细地描述多肽的构象。在本研究中，我们报告了一系列不同标记的螺旋肽的红外光谱。基于重复序列（AAAAK）（n）合成了一系列25聚体肽。我们改变了每个肽上标记的数量和间距，并研究了由于标记位置导致的（12）C和（13）C酰胺I'带的变化。我们的结果表明，改变标记数量会改变（12）C和（13）C酰胺模式的频率和强度。我们还发现，改变标记之间的间距会导致这些酰胺峰发生位移。同位素标记与红外光谱法和理论预测相结合，可能会在残基水平上生成肽主链构象的描述。
