13C nuclear magnetic resonance spectra of fungal melanins

3 pages, 1 figures, 2 tables, 14 references.The 13C resonance spectra of fungal melanins from Aspergillus niger, Eurotium echinolatum, and Stachybotrys chartarum are reported. The spectra were taken in 5% W/W solution of the substances in 0.1 N NaOD in D2O using the Fourier-transform-technique. The spectra and possible assignments of the bands are discussed. The similarities of these spectra to those of soil humic acids are unexpectedly small.Peer reviewe

FT - C13 nuclear magnetic resonance spectra of natural humic substances

The C13 resonance spectra of two humic acids extracted from Vertisol and Andosol soil and of a fulvic acid form Podzol soil are reported. The spectra were taken in 5 % W/W solution of the substances in 0.1 N NaOD in D2O using the Fourier-transform-technique.Peer Reviewe

Dielectric spectroscopy of aqueous solution of fulvic acids

9 pages, 2 figures, 3 tables, 39 references.-- Publicado en el capítulo: Session 1: Isolation, Fractionation, and Characterization.-- Humic Substances in the Aquatic and Terrestrial Environment, Proceedings of an International Symposium, celebrado del 21-23, agosto, 1989 en Linköping, Suecia.-- Este volumen 33, referido en la Citación, consta de 514 páginas, 150 figuras y 57 tablas.The complex dielectric spectrum of aqueous solutions (10% w/w) of fulvic and polymaleic acids has been measured at various frequencies between 1 MHz and 40 GHz. Similar to pure water a dispersion/dielectric loss region emerges in the range above 1 GHz. The measured spectra have been analytically represented by the empirical Cole-Cole relaxation spectral function to yield values for the extrapolated high- and low-frequency permittivity, the principal dielectric relaxation time, the relaxation time distribution parameter and the specific electric d.c. conductivity. In correspondence with aqueous solutions of synthetic organic molecules, the low-frequency permittivity of the fulvic acid/water mixtures is reduced, and the principal dielectric relaxation time is enhanced with respect to the pure water value. As with solutions of polyacrylic acid no solute contributions to the real part of the dielectric spectrum are found.Peer reviewe