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G O Phillips

Publications and source records attributed to G O Phillips.

At least 37 records · Page 2Linked to original sources
PubMed1980

The reactivities of furocoumarin excited states with DNA in solution. A laser flash photolysis and fluorescence study.

The effect of DNA on both the fluorescence emission spectra and yields and lifetimes of the triplet stae of psoralen and 8-methoxypsoralen in aqueous solution has been determined. The changes in the fluorescence spectra are similar in nature for both of these furocoumarins and are attributed to binding of the drug to DNA. The yield of the 8-methoxypsoralen triplet state when bound to DNA was found to be similar, if not identical, to that measured in the absence of DNA. This contrasts sharply with data obtained for psoralen from which it is concluded that either the yield of bound psoralen triplet states is very low, if not zero, or that the lifetime of such species is less than 50 ns. The relevance of this data to the molecular basis of skin photosensitisation by furocoumarins is discussed.

Ficusin↗
PubMed1980

A pulse radiolysis study of the complexing of furocoumarins with DNA and proteins.

The complexing of furocoumarins with DNA in aqueous solution has been investigated using the fast-reaction technique of pulse radiolysis. Association constants are given for 8-methoxypsoralen, psoralen, khellin, angelicin, 5,7-dimethoxycoumarin, 5-methoxypsoralen and 4'-aminomethyl-4,5',8-trimethylpsoralen. In addition, the complexing of some furocoumarins to the protein, bovine serum albumin, has also been studied.

Animals↗
PubMed1980

The determination of the heparin neutralising capacity of protamine using acridine orange fluorescence.

A new method to estimate the heparin neutralising capacity of protamine has been investigated. The technique has been applied to two commercial heparin preparations tested against the W.H.O. 1st International Reference preparation of protamine. The technique is based on the fluorescence of acridine orange dye and the selective binding of heparin with protamine. A titration procedure has been devised and the two variations of the assay are compared and evaluated. The titration is rapid, accurate and convenient.

Acridine Orange↗
PubMed1980

An investigation of calcium ion binding to heparins.

Using the line charge model of Manning and, where appropriate, a form of the empirical corrections to his limiting laws proposed by Wells, we have investigated the ion condensation phenomenon for four pure calcium heparin preparations and similar Ca-heparin/CaCl2 mixtures in aqueous solution. This has been expressed in terms of the single ion activity coefficient of the total calcium counter ion present. The results found for the single counter ion activity coefficient of pure Ca-heparin agree moderately well with the limiting law of Manning for a pure divalent counter ion polyanion salt in dilute solution. The results for Ca-heparin/CaCl2 mixtures when corrected for small ion-small ion interactions give a surprisingly good fit to the theoretical counter ion activity coefficient for a divalent counter ion/divalent cation simple electrolyte system, for values of X (X = the polyanion/co-ion ratio) up to 4, with slight deviations for values of X > 4. In the mixtures with the largest excess of polyelectrolyte, the single ion activity coefficients of the Ca2+ ion are in excess of the value predicted by Manning's theory. Ion exchange of sodium heparins to give the Ca-heparin samples used in the work did not appear to cause regular changes in the anticoagulant activity.

Blood Coagulation↗
PubMed1980

The stigma of Euglena gracilis strain Z: an investigation into the possible occurrence of carotenoproteins and nucleic acids.

Isolated stigmata of light grown cells of Euglena gracilis strain Z were solubilized by a zwitterionic surfactant. The resulting extract was fractionated by gel filtration, and two fractions were obtained. These were then examined for the presence of carotenoproteins and nucleic acids using the techniques of UV/visible spectroscopy, thin layer chromatography and isoelectrofocusing. DNA but not RNA was shown to be present in the high molecular weight fraction, while carotenoid pigments were present in the low molecular weight fraction but they were shown not to be in stoichiometric combination with protein.

Carotenoids↗
PubMed1979

The pH dependence of the reactions of flavin triplet states with amino acids. A laser flash photolysis study.

The pH dependence of the rate constants of reaction of several amino acids with the triplet states of flavin mononucleotide in aqueous solution has been determined. In addition, the relative contributions of hydrogen atom transfer, electron transfer and physical deactivation to the overall process of triplet quenching by amino acids have been estimated. Analogous experiments to those with amino acids were carried out with EDTA as the substrate. The results indicate that the flavin triplet state abstracts an electron from EDTA but does not form an excited state flavin-EDTA complex as suggested in a previous study.

Amino Acids↗
PubMed1979

A laser flash photolysis study of the reactivities of the triplet states of 8-methoxypsoralen and 4,5',8-trimethylpsoralen with nucleic acid bases in solution.

The extinction coefficients, quantum yields and reactivities of the triplet states of 8-methoxypsoralen and 4,5',8-trimethylpsoralen in methanolic solution have been determined using laser flash photolysis techniques. The second-order rate constants for the quenching of these triplet states by pyrimidine and purine bases were found to be several orders of magnitude lower than those found for other furocoumarin derivatives. This may suggest, therefore, that the skin photosensitising ability of such compounds does not necessarily correlate with in vitro triplet state reactivity. Preliminary experiments on the reactivity of the psoralen triplet state with DNA itself indicate that no transient absorptions due to psoralen excited states can be observed when a photon is absorbed by the psoralen-DNA complex.

Carotenoids↗
PubMed1979

Separation and identification of the carotenoid pigments of stigmata isolated from light-grown cells of Euglena gracilis strain Z.

Thin layer chromatography of the carotenoid pigments of stigmata isolated from light grown cells of Euglena gracilis strain Z resolved 29 compounds, of which 16 could be eluted and their absorption spectra recorded. Seven of these compounds were identified by a combination of co-chromatography with authentic compounds and by chemical tests, one of these compounds (beta-carotene) was further identified by mass spectrometry. The major carotenoids were found to be beta-carotene, diatoxanthin and diadinoxanthin which together comprised approximately 60% of the stigma pigments. In addition significant quantities of canthaxanthin, echinenone and cryptoxanthin were isolated and a possible carotenoid ester was detected. The results of this analysis are compared with those of previous workers and the significance of the findings is discussed.

Animals↗
PubMed1978

Analysis of glycosaminoglycans in urine by using acridine orange fluorescence.

The fluorescence technique described here utilizes the electrostatic interaction between the polyanionic sites of glycosaminoglycans and the cationic dye Acridine Orange to analyse urinary glycosaminoglycans from patients suffering from mucopolysaccharidoses. The basis of the titration is the decrease in the fluorescence of free Acridine Orange that occurs when it is bound to polyanions. The effect of the presence of possible interfering materials such as salt, proteins and trace materials in urine was evaluated. This fluorescence technique is technically simple.

Acridine Orange↗
PubMed1978

Effects of ionizing radiations on human costal cartilage and exploration of the procedures to protect the tissue from radiation damage.

The chemical changes produced following 60Co-gamma-irradiation of human costal cartilage have been monitored using "critical electrolyte concentration" (CEC) measurements utilizing Alcian Blue--magnesium chloride and Toluidine Blue--sodium chloride systems. The decrease in the CEC with radiation can be related to the decrease in hexose and hexosamine contents of the cartilage. Such changes arise as a result of degradation of the glycosaminoglycan component of the tissue. The state of the collagen fibres after irradiation has been examined using the Van Giesson stain and by biochemical assay of the hydroxyproline moeity. Energy transfer methods have been utilized to protect the glycosaminoglycan component of the cartilage from radiation damage.

Aged↗
PubMed1978

Interaction of aminoacridines with nucleic acids. A pulse-radiolysis study.

Pulse radiolysis has been used to study the interaction of aminoacridines with nucleic acids. The data confirm that there are two modes of binding. These are: a weak interaction which has a maximum binding ratio of one site per dye; and a strong binding process effected by both electrostatic and Van der Waals interactions. The limit of this latter, strong binding mode is approximately six sites per dye. The radiation-induced transient absorption spectrum of benzoflavine is characterized by a pronounced bleaching at 440 nm, which is quenched by the addition of nucleic acids. Mechanisms have been proposed for the reactions of both eaq-and .OH with benzoflavine which account both for the observed bleaching of benzoflavine solutions and for the protective effect of nucleic acids. It is proposed that eaq-reacts with benzoflavine to form a stable benzoflavine semiquinone radical and that .OH reacts with subsequent formation of a very stable benzoflavine hydroxycyclohexadienyl radical.

Acridines↗