Abstract：
Melanin is a widely distributed and striking dark-colored pigment produced by countless living organisms. Although a wide range of bioactivities have been recognized, there are still major constraints in using melanin for biotechnological applications such as its fragmentary known chemical structure and its insolubility in inorganic and organic solvents. In this study, a bacterial culture of Streptomyces cavourensis SV 21 produced two distinct forms of melanin: (1) a particulate, insoluble form as well as (2) a rarely observed water-soluble form. The here presented novel, acid-free purification protocol of purified particulate melanin (PPM) and purified dissolved melanin (PDM) represents the basis for an in-depth comparison of their physicochemical and biological properties, which were compared to the traditional acid-based precipitation of melanin (AM) and to a synthetic melanin standard (SM). Our data show that the differences in solubility between PDM and PPM in aqueous solutions may be a result of different adjoining cation species, since the soluble PDM polymer is largely composed of Mg2+ ions and the insoluble PPM is dominated by Ca2+ ions. Furthermore, AM shared most properties with SM, which is likely attributed to a similar, acid-based production protocol. The here presented gentler approach of purifying melanin facilitates a new perspective of an intact form of soluble and insoluble melanin that is less chemical altered and thus closer to its original biological form.
摘要：
黑色素是一种分布广泛且引人注目的深色色素，由无数生物体产生。尽管已经认识到广泛的生物活性，在将黑色素用于生物技术应用中仍然存在主要限制,例如其已知的化学结构及其在无机和有机溶剂中的不溶性。在这项研究中,的细菌培养的链霉菌SV21产生两种不同形式的黑色素：（1）颗粒，不溶性形式以及（2）很少观察到的水溶性形式。这里介绍的小说，纯化颗粒黑色素（PPM）和纯化溶解黑色素（PDM）的无酸纯化方案代表了深入比较其物理化学和生物学特性的基础，将其与传统的基于酸的黑色素沉淀(AM)和合成黑色素标准(SM)进行比较。我们的数据表明，PDM和PPM在水溶液中的溶解度差异可能是不同相邻阳离子种类的结果，由于可溶性PDM聚合物主要由Mg2离子组成，而不溶性PPM主要由Ca2离子组成。此外，AM与SM共享大多数属性，这可能归因于类似的，基于酸的生产协议。这里提出的更温和的纯化黑色素的方法促进了可溶性和不溶性黑色素的完整形式的新观点,其化学变化较小,因此更接近其原始生物形式。
