Costentino M, Pritzker L, Boulias C, Moscarello M A
Hospital for Sick Children, Toronto, Ontario, Canada.
Biochemistry. 1994 Apr 12;33(14):4155-62. doi: 10.1021/bi00180a008.
A peptide consisting of the first 21 residues of human myelin basic protein (MBP) was synthesized. The N-terminal alanine of portions was blocked in separate experiments with alkyl carboxylates varying in size from 2 to 10 carbon atoms. The effects of these different alkyl carboxylates at the N-terminus on the secondary structure was studied by circular dichroism (250-190 nm). In water, the spectra of the unblocked peptide suggested unordered structure with large negative ellipticities at 198 nm. Addition of an acetyl group altered the magnitude of [theta]198 from -21856 +/- 2319 to -11095 +/- 1000 deg cm2 dmol-1, suggesting a significant increase in ordered structure. When peptides with longer alkyl carboxylates, acylated at the N-termini, were studied, the magnitude of theta 198 approached that of the unblocked peptide but greater negative ellipticities were observed for the C8 and C10 alkyl carboxylates. The theta 222 values were generally low (-1803 +/- 463) but increased with increasing length of the alkyl carboxylate to about -3200 deg cm2 dmol-1, suggesting that little alpha-helical structure was present. The spectra were also taken in lipid-mimetic solvents, including 2-propanol, methanol, and lysophosphatidylglycerol (lysoPG). In general the theta 198 and theta 222 values were suggestive of increased structure in these environments compared to water. In 90% 2-propanol the theta 198 of the unblocked peptide did not change when an acetyl group was added to the N-terminus (9088 compared to 8477 deg cm2 dmol-1). Addition of longer alkyl carboxylates correlated with larger, negative ellipticities.(ABSTRACT TRUNCATED AT 250 WORDS)
合成了一种由人髓鞘碱性蛋白（MBP）前21个残基组成的肽。在不同实验中，用碳原子数从2到10不等的烷基羧酸盐对该肽部分片段的N端丙氨酸进行封闭。通过圆二色性（250 - 190 nm）研究了N端这些不同烷基羧酸盐对二级结构的影响。在水中，未封闭肽的光谱表明其结构无序，在198 nm处有较大的负椭圆率。添加乙酰基后，[θ]198的值从-21856±2319变为-11095±1000度·厘米²·dmol⁻¹，表明有序结构显著增加。当研究N端被较长烷基羧酸盐酰化的肽时，θ198的值接近未封闭肽，但对于C8和C10烷基羧酸盐观察到更大的负椭圆率。θ222的值通常较低（-1803±463），但随着烷基羧酸盐长度增加而增加至约-3200度·厘米²·dmol⁻¹，表明几乎不存在α-螺旋结构。还在模拟脂质的溶剂中进行了光谱测定，包括2-丙醇、甲醇和溶血磷脂酰甘油（lysoPG）。总体而言，与水相比，这些环境中的θ198和θ222值表明结构有所增加。在90%的2-丙醇中，当向未封闭肽的N端添加乙酰基时，θ198没有变化（分别为9088和8477度·厘米²·dmol⁻¹）。添加较长烷基羧酸盐与更大的负椭圆率相关。（摘要截断于250字）
