THE PHOTOSENSITIZED OXIDATION OF TYROSINE REACTION UNDER HOMOGENEOUS CONDITIONS DERIVATIVES IN THE PRESENCE OF ALGINATE-I

Abstract —The rates of dye-sensitized photooxidation of tyrosine and tyramine to brown products were compared in the presence and the absence of the anionic polysaccharide, alginate. The polyelectrolyte did not affect the reaction when it was sensitized by monochromatic light absorbed mainly by the monomeric form of the dye. In white light, the rate of oxidation sensitized by thionine or phenosafranine was increased in the presence of alginate for tyramine, but not for tyrosine. In the thionine sensitized reaction, the ratio of brown product formation to tyramine consumption increased with decreasing wavelength of monochromatic excitation. These and other phenomena are believed related to the formation of complexes between the dyes and some of the oxidation products, and to association between some of the oxidation products and alginate. A mechanism for oxidation of phenols is proposed, based on the addition of O₂ (¹Δ9) across a double bond ortho to the phenolate oxygen. Dyes bind to alginate in monomeric and in aggregated forms; only the monomeric forms of thiazine dyes are photochemically active, but both the monomeric and the aggregated forms of crystal violet are active.     

Nuclear relaxation studies of the spin-Peierls transition

Nuclear relaxation studies of the spin-Peierls transition in TTF-BDT are presented. At low temperature, but above T_c, the results agree in magnitude, frequency dependence and temperature dependence with calculations based on the pseudofermion treatment of the $\text{S =}\text{1}\text{2}$, 1-D Heisenberg antiferromagnet. The sharp decrease in the rate below T_c reflects the continuous opening of a magnetic energy gap at the spin-Peierls transition.     

A fourier transform infrared spectroscopic investigation of polyethylene single crystals. II. Fine structure of the CH2 rocking mode

The application of the spectral subtraction routine to an analysis of the CH₂ rocking mode of polyethylene single crystals is discussed. A difference band at 716 cm^?1 characteristic of a local monoclinic arrangement of chains is detected. Oxidation of crystal mats by nitric acid indicates that these defect structures are located inside the crystal and are not associated with the fold surface.     

Optimization of automatically generated rules for predicting the presence and absence of substructures from MS and MS/MS data

A pattern-recognition/artificial-intelligence program, referred to as MAPS (Method for Analyzing Patterns in Spectra), was recently developed to identify the relationships that exist between substructures and the characteristic features they produce in the spectra from mass spectrometry (MS) and successive mass spectrometry (MS/MS). MAPS has been extended to utilize these relationships to formulate exclusion rules as well as inclusion rules, so that the absence of recognized substructures can be predicted as well as their presence. The potential usefulness of each MS and MS/MS spectral feature in such rule formulation is characterized by correlation and uniqueness factors. The correlation factor expresses the degree of correlation between a feature and a specific substructure; the uniqueness factor expresses the uniqueness of a feature with respect to that substructure. Features with high correlation factors are most use for predicting the absence of substructures, whereas features with high uniqueness factors are most useful for predicting their presence. Feature intensity-data have been found to improve the inclusion-rule performance and degrade the exclusion-rule performance. Criteria for optimizing the predictive abilities of both rule types are discussed.