Browsing by Author "SALIMHANNA, M"

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    OBTENTION OF A PHOTOINDUCED ADDUCT BETWEEN A VITAMIN AND AN ESSENTIAL AMINO-ACID - BINDING OF RIBOFLAVIN TO TRYPTOPHAN
    (1987) SALIMHANNA, M; EDWARDS, AM; SILVA, E
    Studies in animals have suggested that the products of the irradiation of tryptophan in the presence of riboflavin may play a role in the development of hepatic dysfunction during parenteral nutrition. In this paper we describe the formation of an adduct between tryptophan and riboflavin obtained as a consequence of an anaerobic irradiation of these compounds. Through the use of molecular sieves and of an ion-exchange resin it was possible to separate the photo-adduct from the dimer riboflavin and other reaction products. The various fractions were characteized on the basis of their absorption and emission spectra. Also used were measures of anisotropy of fluorescence emission in order to characterize the derived adduct.
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    RIBOFLAVIN STATUS AND PHOTOINDUCED RIBOFLAVIN BINDING TO THE PROTEINS OF THE RAT OCULAR LENS
    (1988) SALIMHANNA, M; VALENZUELA, A; SILVA, E
    The presence of radioactivity in lenses of rats injected intraperitoneally with a solution of tryptophan and 14C-riboflavin, irradiated during 48 hours and under N2 atmosphere, was detected. The excitation fluorescence spectrum (.lambda.emission = 520 nm) of the soluble lens fraction corresponds to the riboflavin decomposition product of lumichrome type. When 14C-riboflavin enriched lenses were exposed to visible light, a photo-induced binding between riboflavin and a water insoluble protein fraction of the lenses was observed. This finding may help to clarify the lens modifications during aging and in cataractogenesis.
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    TOXIC EFFECT OF A PHOTOINDUCED TRYPTOPHAN-RIBOFLAVIN ADDUCT ON F9-TERATOCARCINOMA CELLS AND PREIMPLANTATION MOUSE EMBRYOS
    (1988) SILVA, E; SALIMHANNA, M; BECKER, MI; DEIOANNES, A
    Solutions containing L-tryptophan and riboflavin exposed to visible light, under N2 atmosphere, yield a tryptophan-riboflavin adduct, able to inhibit the growth of cultured F9 teratocarcinoma cells. This same effect was found in the presence of a mixture of the tryptophan photooxidation products and the adduct, when using solutions previously irradiated with visible light in an O2 atmosphere. A cytotoxic effect was also observed with embryos incubated in the presence of a tryptophan-riboflavin adduct, in the latter case necrosis and embryo development arrest occured.