Spectroscopic Studies of Melanin.
Abstract
To gain insight into the photochemistry of melanin, we have measured chemiluminescence and Raman spectra of synthetic tyrosine melanin. Chemiluminescence kinetics were obtained from a sealed capillary tube containing a basic melanin solution. Excitation at 488.0 nm and monitoring emission at 633 nm produced a first order rise and a second order decay in intensity to steady state levels. We collected steady state emission spectra from a flow system excited by argon ion and helium-neon laser radiation. The full width at half maximum, position, and intensity of fluorescence were measured. The full width at half-maximum (3600/cm) was independent of excitation wavelength. At higher energy excitation, the emission maximum was independent of excitation line. At lower energy excitation, the emission maximum varied with the excitation line. The emission intensity dropped by a factor of 6 as the excitation wavelength was varied from 465.8 nm to 514.5 nm. Luminescence was also observed upon excitation at 632.8 nm of melanin dissolved in DMSO. Raman data, obtained from solid melanin suspended in a KBr pellet (rotating sample cell, 488.0 nm excitation, 5/cm band pass), revealed broad bands at 1385/cm, 1590-1615/cm and 2930/cm superimposed upon a weak fluorescent background. Upon ultraviolet laser excitation (363.8 nm, 5 mW power on the sample, 5/cm band pass), a single broad band appeared, centered at 1300/cm. The difference from visible excitation implies that resonance enhancement from an ultraviolet absorbing chromophore occurred.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1986
- Accession Number
- ADA168242
Entities
People
- David L. Bolton
- Elmar T. Schmeisser
- Steven T. Schuschereba
- Thomas M Cooper