Self-assembly of melanin studied by laser light scattering

被引:43
作者
Bridelli, MG
机构
[1] Univ Parma, INFM, I-43100 Parma, Italy
[2] Univ Parma, Dept Phys, I-43100 Parma, Italy
关键词
melanin; light scattering; polymerization; hydrodynamic radius; radius of gyration; fractal dimension;
D O I
10.1016/S0301-4622(98)00148-3
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The unknown molecular weight and chemical structure of melanin place the study of these pigments outside the range of the classical biochemical techniques; thus in this paper the problem of characterizing these heterogeneous biopolymers was approached by means of light scattering techniques, static and dynamic. The static technique allowed us to identify the macromolecular properties ([MW] and [R-g(2)](1/2)) of melanin extracted from sepia inksac and of two synthetic analogues: L-Dopa melanin obtained by autooxidation and by enzymatic oxidation by Tyrosinase. By dynamic light scattering (DLS), the hydrodynamic radius Rh was measured to monitor the temporal behaviour of the polymerization and aggregation processes and R-h variation by changing the chemical constraints of the polymerization medium, such as pH and ionic strength. The fractal dimension d of the aggregates of melanin, both natural and synthetic, in the past only recognized during the aggregation of the synthetic one by lowering the pH of the medium, was a useful parameter to further investigate and compare the structure of melanin granules of differing origins, revealing for the natural sample, a structure with clusters that are spherical, not largely hydrated and self-assembled, following a reaction limited aggregation kinetics (d = 2.38) (C) 1998 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:227 / 239
页数:13
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