SOMATOSTATIN IN A WATER-RESTRICTED ENVIRONMENT - FLUORESCENCE AND CIRCULAR-DICHROISM STUDY IN AOT REVERSE MICELLES

被引：12

作者：

BHATTACHARYYA, K ^{[1
]}

BASAK, S ^{[1
]}

机构：

[1] SAHA INST NUCL PHYS,DIV NUCL CHEM,CALCUTTA 700064,W BENGAL,INDIA

来源：

PHOTOCHEMISTRY AND PHOTOBIOLOGY | 1995年 / 62卷 / 01期

关键词：

D O I：

10.1111/j.1751-1097.1995.tb05232.x

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 [生物化学与分子生物学]; 081704 [应用化学];

摘要：

Steady-state and time-resolved fluorescence emission from the single tryptophan residue of somatostatin, and the kinetics of quenching of this emission, were studied in aqueous solution and in reverse micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/water/isooctane, a system that mimics the water-membrane interface well. Incorporation into micelles caused blue shifts and reduced bandwidths of the emission peaks and altered the quantum yields with respect to emission from bulk water. Steady-state anisotropy values also increased considerably on micellization. These observations point to reduced polarity of the environment around the Trp residue of the peptide, as well as restricted freedom of its rotational motions, due to transfer from the aqueous to the micellar phase. Fluorescence emission kinetics of the Trp moiety followed biexponential decay laws in both aqueous and micellar media. Static and dynamic quenching constants were measured for acrylamide and CCl4 quenchers localized in the micellar and organic pseudophases, respectively, using both steady-state and time-resolved experiments. The efficiency of dynamic quenching by acrylamide became vanishingly small in going from water to reverse micelles, in sharp contrast to the comparable quenching efficiencies exhibited by CCl4 in micelles and acrylamide in water. The circular dichroic (CD) spectrum of the native peptide in water indicated the possibility of some amount of beta-type secondary structure being present. Conformational analysis of CD spectra in micelles showed that the relative amount of this structural feature was enhanced for the micellized peptide but was insensitive to the water content of micelles. The above results, put together, indicate that the Trp-8 residue in somatostatin is likely to be located in the close neighborhood of the water-AOT molecular interface, where the water molecules are strongly immobilized. This work also demonstrates the role of reverse micelles as a convenient membrane-mimetic medium for the study of membrane interactions of bioactive peptides.

引用

页码：17 / 23

页数：7

共 27 条

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