Fretheim K, Egelandsdal B, Harbitz O
Int J Pept Protein Res. 1985 Jun;25(6):601-7. doi: 10.1111/j.1399-3011.1985.tb02216.x.
Conformational changes induced in ovomucoid, lysozyme and ovotransferrin on reductive addition of different sized substituents have been studied employing differential scanning calorimetry (DSC) and circular dichroic spectroscopy (CD). The thermograms obtained by DSC revealed that extensive introduction of methyl, isopropyl, cyclopentyl, cyclohexyl, benzyl or n-butyl groups has a detrimental effect on thermal stability (enthalpy of denaturation); the effect generally increases with the size of the substituent. Circular dichroic spectra were affected only to a very limited extent by the modifications, near-u.v. spectra remaining much the same while far-u.v. spectra displayed minor changes. The general conclusion drawn is that the modifications had only limited effects on the conformation of the proteins while, nonetheless, perturbing (or breaking) long-range intramolecular interactions so as to destabilize the structure. Derivatization of lysozyme and ovotransferrin with some of the larger groups has been reported to result in spontaneous precipitation of the proteins [Fretheim, K., Iwai, S. & Feeney, R.E. (1979) Int. J. Peptide Protein Res. 14, 451-456]. The present investigation indicates that precipitation was caused by (partial) denaturation (and ensuing aggregation) as a consequence of modification.
利用差示扫描量热法（DSC）和圆二色光谱法（CD），研究了在还原添加不同大小取代基时，卵类黏蛋白、溶菌酶和卵转铁蛋白中诱导的构象变化。DSC获得的热谱图显示，大量引入甲基、异丙基、环戊基、环己基、苄基或正丁基对热稳定性（变性焓）有不利影响；这种影响通常随取代基大小的增加而增大。修饰对圆二色光谱的影响非常有限，近紫外光谱基本保持不变，而远紫外光谱显示出微小变化。得出的一般结论是，修饰对蛋白质的构象只有有限的影响，然而，却扰乱（或破坏）了长程分子内相互作用，从而使结构不稳定。据报道，用一些较大的基团对溶菌酶和卵转铁蛋白进行衍生化会导致蛋白质自发沉淀[弗雷泰姆，K.，岩井，S. & 费尼，R.E.（1979年）《国际肽与蛋白质研究杂志》14卷，451 - 456页]。本研究表明，沉淀是由修饰导致的（部分）变性（以及随后的聚集）引起的。
