Post by skyship on Jan 11, 2014 1:32:33 GMT -5
A little leprae?
Utilization of indole compounds by Cryptococcus neoformans to produce a melanin-like pigment.
Several indoles served as substrates for the phenoloxidase of Cryptococcus neoformans and resulted in the production of a melanin-like pigment. In general, a higher percentage of C. neoformans var. neoformans (A and D serotypes) isolates could produce pigment from indoles than could those of var. gattii (B and C serotypes). Only compounds with a hydroxyl or an amino group on the phenyl ring produced pigment; methoxy, nitro, methyl, and fluorine substituents on the phenyl ring were inactive, as was a hydroxyl group at the 2 position on the indole ring. The phenoloxidase of C. neoformans thus appears to differ from that found in Mycobacterium leprae, which cannot use a hydroxyindole, desoxyfructo-5-hydroxytryptamine, as a substrate. In addition, C. neoformans differs from M. leprae in that desoxyfructo-5-hydroxytryptamine does not inhibit the uptake of dihydroxyphenylalanine into the cell.
www.ncbi.nlm.nih.gov/pmc/articles/PMC272919/
================================================
Link 6-DHI-melanin
www.tightrope.it/nicolaus/index.htm
Key words: melanins, fullerenes, cosmids, MALDI, conducting polymers, X-ray diffraction, DHI-melanin, black particles, tensegrity.
Melanins ( 1 ) constitute an insoluble and infusible material difficult to purify
Black material could have origin from different molecules called melanogens. These are on earth, generally, hydroxylated aromatic compounds (orto.diphenols) of aromatic systems like benzene, indole, pyrrole, pyridine, quinoline. Substances of biological interest having the property generating black particles are DOPA, Cyclodopa, DHI (5,6-dihydroxindole), DHICA (5,6-dihydroxindole-2-carboxylic acid), dopamine, adrenaline, serotonin, 5,6-hydroxytryptamine [2], 6,7-dihydroxy-1-metil-tetrahydroisoquinoline (salsolinol) [3]. All the substances could, in different conditions, generate black materials. The chemical study of sepiomelanin indicate cyclodopa (leucodopachrome) as precursor. It is generally believed that DHI and DHICA are the precursors of pigment cell. The particles (in biology granules) present themselves generally under ovate or globular shape (rugby or soccer ball) and are built up from the precursor’s oligomers. It is possible that these materials constitute cage systems of giant fullerene type or graphite - like stacking spacing of 3.45 A, 4-5 layers thick.The first phase consists of the formation of policonjugated chains the so called Little's spine [4]. It must be observed that the spine alone can result dielectric. But if opportunely substituted from quaternary lateral groups in which the charge could interact with the electrons moving in the spine the superconductive state is produced, i.e. a distinctive organic macromolecule with superconductive properties in agreement with the BCS theory [5] is formed. It is curious that in Little's model the spine was acetyleneblack and the lateral chains were constituted by diethylcyanine iodide, a well known light-sensitive compound.The structures formed from 16 (magic number ?) DHI units is reported. The structures, among those possible, differ for the presence of furane rings. These structures are theoretically semiconductors [7] or superconductors [5].The second phase of oligomerization is characterized by self-assembling of the different units up to achieve a particle.The first phase could be verified examining the reaction products by MALDI and MALDI-TOF mass spectrometry .It was suggested that indole oligomers could be formed until 11 units by oxidizing dopamine with peroxidase/H2O2 and until 8 by oxidizing tyrosine with tyrosinase [2a], [6]
www.tightrope.it/nicolaus/11b.htm