Characterization of free aromatic amino acids and estimation of exposition rate of phenylalanine in casein hydrolysates by second derivative spectrophotometry.

In this work, the second derivative spectrophotometry (SDS), a fast, simple and relatively low-cost method,-was used to characterize aromatic amino acids at two pH values (7 and 13) and to evaluate the exposition rate of Phe in casein hydrolysates prepared with papain. The results indicate that at 37 degrees C, pH 7.5 and an enzyme:substrate ratio of 4:100, for hydrolyzing casein by papain, the highest Phe exposition was observed. Therefore these are the most appropriate conditions for Phe removal and preparation of supplements for phenylketonurics. The use of SDS at pH 13.0 gives a good resolution of Tyr and Trp peaks. A similarity among SDS spectra of aromatic amino acids and protein hydrolysates, was also observed.

Addition effects of bovine blood globin and sodium caseinate on the quality characteristics of raw and cooked ham pâté.

The incorporation of 3% globin bovine extracted by the acidified acetone (AG) and carboxymethylcellulose (CG) methods as replacer for sodium caseinate (CA) in ham pâté was evaluated. The raw pâté batter was evaluated for salt-soluble protein content (SSP), water holding capacity (WHC) and raw batter stability (RBS). The results of CG were similar to those of CA, having both improved two of the three paramaters studied, and AG was the most deleterious, having decreased SSP, WHC and RBS. Only the AG incorporation had unfavorable effects on the cooked ham pâté, decreasing the pH and increasing the thiobarbituric acid reactive substances (TBARS) over the storage period (0-45 days). The results suggest CG as the best replacer for CA as the emulsifying agent for ham pâté.

Controlling Electronic Communication in Ethynylated-Polypyridine Metal Complexes.

By introduction of a naphthalene subunit in the middle of a butadiynylene spacer the triplet lifetime of the ruthenium chromophore in RR is prolongated to 475 ns. By increasing laser intensities the two Ru-terpy terminals are simultaneously promoted to the triplet state, and triplet - triplet annihilation occurs. In contrast, in the mixed Ru/Os complex (RO) the long inherent triplet lifetime of the Os-terpy fragment facilitates reverse triplet energy transfer. terpy=bis(2,2':6',2"-terpyridine).

Mono- and dinuclear ruthenium(II) and osmium(II) polypyridine complexes built around spiro-bridged bis(phenanthroline) ligands: synthesis, electrochemistry, and photophysics.

Two new dyads have been synthesized in which terminal Ru(II) and Os(II) polypyridine complexes are separated by sterically constrained spiro bridges. The photophysical properties of the corresponding mononuclear complexes indicate the importance of the decay of the lowest-energy triplet states localized on the metallo fragments through the higher-energy metal-centered excited states. This effect is minimized at 77 K, where triplet lifetimes are relatively long, and for the Os(II)-based systems relative to their Ru(II)-based counterparts. Intramolecular triplet energy transfer takes place from the Ru(II)-based fragment to the appended Os(II)-based unit, the rate constant being dependent on the molecular structure and on temperature. In all cases, the experimental rate constant matches surprisingly well with the rate constant calculated for Förster-type dipole-dipole energy transfer. As such, the disparate rates shown by the two compounds can be attributed to stereochemical factors. It is further concluded that the spiro bridging unit does not favor through-bond electron exchange interactions, a situation confirmed by cyclic voltammetry.

Gadolinium(III) texaphyrin: a tumor selective radiation sensitizer that is detectable by MRI.

Gadolinium(III) texaphyrin (Gd-tex2+) is representative of a new class of radiation sensitizers detectable by magnetic resonance imaging (MRI). This porphyrin-like complex has a high electron affinity [E1/2 (red.) approximately = -0.08 V versus normal hydrogen electrode] and forms a long-lived pi-radical cation upon exposure to hydrated electrons, reducing ketyl radicals, or superoxide ions. Consistent with these chemical findings, Gd-tex2+ was found to be an efficient radiation sensitizer in studies carried out with HT29 cells in in vitro as well as in in vivo single and multifraction irradiation studies with a murine mammary carcinoma model. Selective localization of Gd-tex2+ in tumors was confirmed by MRI scanning.

In vitro and in vivo growth suppression of MCF-7 human breast cancer by novel photoproducts and tamoxifen.

BACKGROUND: Preactivation is a novel photochemical method for the production of chemotherapeutic compounds that exert their biologic effects independent of light. The compounds that are produced, preactivated merocyanine 540 (pMC540) and merodantoin, are cytotoxic to cultured human breast cancer cells but are only minimally cytotoxic toward normal cells. Their effects against breast cancer have not been studied in vivo. METHODS: Estrogen-stimulated human MCF-7 breast adenocarcinoma cells were grown as solid tumors in athymic carrier mice. Animals bearing defined sizes of subcutaneously transplanted solid breast tumors received injections of pMC540 (250 mg/kg) with or without concurrent treatment with tamoxifen. Growth inhibitory effects of merodantoin (N,N'-dibutyl-2-thio-4,5-imidazolidion) on the breast tumor growth were determined. RESULTS: Direct injection of established tumors with eight doses of pMC540 (250 mg/kg) administered on alternate days resulted in significant tumor regression (P = 0.002). In three of seven animals, palpable tumors could not be detected after this treatment (16 days). Treatment through intramuscular injections (20 doses) with pMC540 (250 mg/kg) also caused a significant suppression of tumor area (P = 0.004; P = 0.0882; P = 0.0903) and a marginally significant suppression of tumor weight and volume, respectively. Combined treatment with tamoxifen and pMC540 (100 mg/kg) caused a 67% suppression of breast tumor growth. Treatment with 20 doses of merodantoin (75 mg/kg) suppressed the growth of breast tumors by 98%. CONCLUSION: To the authors' knowledge, these results show for the first time that photochemically generated novel compounds in pMC540 alone and in combination with tamoxifen are effective in suppressing in vivo growth of xenografted human MCF-7 breast tumors.

Contributions to the history of psychology: XCV. Possible relations between theories of evolution and animal learning.

It is proposed that the dominance of continuity learning theory as set against noncontinuity learning theory during the middle third of the 20th century rested importantly on its derivation from Darwin's theory of evolution. The kinship is shown in several ways. First, Thorndike and Hull echoed the principle of natural selection in their belief that behaviors underwent gradual modification because acts that were attended steadily by favorable consequences tended to occur with increasing frequency. Second, they denied both nonphysical explanations of behavior and a priori purposes which might guide that behavior. Third, the laws of learning were said to hold for all organisms. It is argued that the continuity approach may have enjoyed success because it was consistent with the Darwinian world view. Had punctualist, rather than gradualist, explanations of evolution come to the fore in the late 19th century, learning theories might have proceeded quite differently with the dominance of non-continuity approaches.

Preactivation: a new concept for generation of photoproducts for potential therapeutic applications.

Controlled exposure of photoactive compounds to light prior to their use in biological targets results in the formation of heretofore unknown photoproducts. This process of photoproduct generation, termed preactivation, renders the photoactive compound capable of systemic use without further dependence on light. We have demonstrated that preactivated Merocyanine and preactivated Photofrin-II possess significant antitumor and antiviral activity against certain tumor cells and viruses, while under identical conditions normal cells and tissues are minimally affected. Thus, the preactivation procedure may represent a promising therapeutic modality for controlling systemic malignancies and viral infections.

Protein damage by photoproducts of merocyanine 540.

Exposure of certain photoactive dyes to light prior to their use in biological systems (preactivation) has been shown to result in formation of long-lived cytotoxic photoproducts. The cytotoxic species responsible for the biological activity of preactivated merocyanine 540 (pMC540) appears to be a hydroperoxide generated by oxidation of ground-state dye by singlet molecular oxygen, formed via energy transfer from triplet excited-state dye to oxygen. A positive correlation (r = .93) exists between the levels of hydroperoxides and percent of tumor cells killed upon exposure to pMC540. Exposure of bovine serum albumin (BSA) (0.5 mg/mL) to pMC540 (0.2 mg/mL-1 mg/mL) results in loss of tryptophan fluorescence and 345 nm emission, suggesting a probable role of either hydroxyl (.OH) or .OH + superoxide (O2-). Polyacrylamide gel electrophoresis indicates fragmentation of treated BSA. Aggregation of pMC540-treated BSA is not detected. Bityrosine production is not observed. A dose-dependent decrease in BSA solubility is observed in treated samples, suggesting an increase in hydrophobicity. Amino acid analysis of BSA treated with pMC540 shows loss of some amino acids residues. The data presented here suggest that photoproducts of MC540 derived via the process of preactivation may mediate their effect (at least in part) by reactive oxygen species.

Photochemistry of merocyanine 540: the mechanism of chemotherapeutic activity with cyanine dyes.

The photophysical properties of merocyanine 540 have been determined in methanol solution over a modest temperature range. Triplet state population is inefficient (the limiting triplet quantum yield being 0.25) due to rapid isomerization of the central double bond from the first excited singlet state. Activation energies have been measured for isomerization from the excited singlet state (20 kJ mol-1) and for conversion of the resultant cis-isomer back to the original trans-form (63 kJ mol-1), both processes involving formation of a twisted species. The dye is easily oxidized to give an unstable adduct which decomposes on the sub-ms timescale. Reversible redox chemistry occurs upon excitation in the presence of electron acceptors. These various observations are discussed in terms of the known chemotherapeutic activity of MC540 and it is concluded that the most probable mechanisms for cytotoxicity involve either local thermal disruption of cell membranes or in situ photogeneration of toxins derived from breakdown of the dye.

In vitro photodynamic activity of kryptocyanine.

The photophysical properties of 1,1'-diethyl-4,4'-carbocyanine chloride (kryptocyanine) have been measured in methanol solution and for the dye bound to human serum albumin, incorporated in neutral micelles and after incubation with leukemia cells. In all cases, it is found that formation of the triplet state of the dye occurs with low efficiency and that illumination of the dye under aerobic conditions does not produce significant yields of O2(1 delta g). Instead, the only efficient photoprocess involves rapid internal conversion from the first excited singlet state to the ground state, probably via isomerization of the polymethine sequence. These findings are discussed with respect to the demonstrated ability of kryptocyanine to photodestroy leukemic cells.

Solution acceptance by common ravens (Corvus corax) given two-bottle preference tests.

Two-bottle tests of solution acceptance were conducted in an outdoor aviary with eight common ravens (Corvus corax). Aqueous concentrations of the following chemicals were used: five common sugars, three salts, two acids, quinine hydrochloride, and sodium saccharin. Solution acceptance, as recorded for the different ravens on each test, was the percentage of preference shown for a test solution over water (comparison solution). Mid-range saccharin concentrations (0.10% to 0.80% [w/w]) were preferred over water in the tests. The preference for saccharin contrasts with all other reports on avian response to the chemical in two-bottle tests. Nonetheless, the ravens nonpreferentially accepted lower concentrations or were averse at higher concentrations to drinking sugar solutions. Similar, though more sharply marked, shifts from indifference to aversion were noted in tests with the other chemicals. The possible relevance of these latter findings to the food habits of ravens is discussed.

Reduction reactions of water soluble cyano-cobalt(III)-porphyrins: metal versus ligand centered processes.

Reduction reactions of dicyano-cobalt(III)-porphyrins [potential in vivo cyanide scavenger drugs] were studied by radiolytic and electrochemical methods using the water soluble tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP). For [(CN)2CoIIITPPS]-, reduction occurs stepwise to the CoII, CoI, and finally to the phlorin anion. This behavior is similar to that of the cobalt porphyrins in the absence of cyanide, except that the cyanide ligand shifts the reduction potentials to much more negative values. On the other hand, under radiolytic conditions, [(CN)2CoIIITMPyP]- is reduced on the porphyrin macrocycle by one electron to give the CoIII pi-radical anion, which disproportionates into the initial complex and the two-electron ring reduced CoIII phlorin. The radical anion is also formed by intramolecular electron transfer subsequent to the reaction of CoIITMPyP and cyanide. The results are compared with the chemistry of Vitamin B-12.

Photoreactions of macrocyclic dyes bound to human serum albumin.

The photophysical properties of tetrakis(4-sulfonatophenyl)porphyrin (H2TSPP), its tin (IV) complex (SnTSPP), aluminium(III) trisulfonatophthalocyanine (AIPCS), and the corresponding zinc(II) complex (ZnPCS), have been measured in H2O, D2O, and upon binding to human serum albumin (HSA). The triplet excited states of the various macrocyclic dyes generate singlet molecular oxygen, O2(1 delta g) in high quantum yield upon illumination in O2-saturated solution, even in the presence of HSA. The triplet states also abstract an electron from 4-aminophenol, forming the radical anion of the macrocycle. Quenching rate constants and quantum yields have been measured for the various processes in the presence and absence of HSA. It is found that HSA binds all the dyes at nonspecific sites close to the interface in such a manner that the dyes remain accessible to species residing in the solution phase. Dyes that do not possess axial ligands complexed to the central cation (e.g. H2TSPP, ZnPCS) are able to bind also at a deeper, more specific site on the protein where they are protected from species in solution. Under such conditions, triplet quenching by 4-aminophenol is restricted to long-distance electron tunnelling, for which the rate is relatively slow.

Photosensitized oxidation of biomaterials and related model compounds.

Aluminium trisulfonatophthalocyanine (A1PCS), a dye being widely advocated for use in photodynamic therapy, produces singlet oxygen with a quantum yield of 0.34 in oxygenated water at pH 7. Triplet A1PCS abstracts an electron from a variety of amines and phenols, the rate of electron transfer depending upon the thermodynamic driving force, forming the A1PCS radical anion. This latter species reduces molecular oxygen to superoxide ions with high efficiency. The triplet state also abstracts an electron from biological components, including NADH, vitamin C, cysteine, methionine, tyrosine, tryptophan, uracil, and guanine, but not from DNA. These results suggest that photoinduced electron abstraction from appropriate biomaterials could compete with singlet oxygen production under in vivo conditions.

Dietary pyridoxine loadings affect incidence of "spontaneous" seizures among magnesium-deprived Mongolian gerbils (Meriones unguiculatus).

The "spontaneous" tetanic attacks in magnesium (Mg) deficiency resemble those occurring in pyridoxine (Pyr) deficiency. A common mechanism may underlie both seizure patterns. Nine groups (n = 10) of male Mongolian gerbils that were Mg-deprived, Pyr-deprived, or both were used to explore this possibility. The animals were tested for spontaneous seizing in an open field at four-day intervals over 40 days. By the end of the period, 70% of the gerbils that were both Mg- and Pyr-deprived had seized, and 90% had died. One fatality, but no seizures, occurred among Pyr-deprived groups given 500 to 2,000 ppm Mg in the food. No seizures occurred among the Mg-deprived groups fed 20 to 100 ppm Pyr, though several animals given 20 ppm Pyr died. Deaths and seizures occurred within Mg-deprived groups fed more than 100 ppm Pyr. A possible role of Pyr in Mg metabolism is discussed.

Harderian gland exudates in the male Meriones unguiculatus regulate female proceptive behavior, aggression, and investigation.

Harderian gland secretions exit from the nose of Meriones unguiculatus during an autogroom (Thiessen, 1977). The exudates act as an attractant pheromone and as a thermoregulatory barrier when spread throughout the pelage. A recent study demonstrated that Harderian exudates in the male guide proceptive behavior in the female (Harriman & Thiessen, 1985). The present study replicated this finding by showing that estrous females direct fewer proceptive acts toward males lacking Harderian glands. In addition, it was found that females are more defensively aggressive toward Harderianectomized males and prefer to spend more time in the vicinity of intact males. It is speculated that Harderian spread allows the female to assess the reproductive competence of the male.

Olfactory acuity in the common raven (Corvus corax).

The efficacy with which ravens can locate concealed carrion and similar foods has been noted from antiquity. This ability has been claimed in folklore to indicate an acute sense of smell. Contemporary opinion among ornithologists is that the sense of smell is weak at best in passerines, and particularly so in corvids which lack developed olfactory apparatus. Four studies were performed to test whether ravens could find hidden food (fresh ground fish) under conditions where scent was presumed to be the sole cue. The subjects, captive juvenile ravens (five males and three females) capably chose which one in a pair of containers held food buried under 2.0 cm of No. 4 gravel, discovered food concealed under as much as 2.5 cm of gravel, and located as little as 1.0 g of food covered by 1.5 cm of gravel. The several findings are consistent with the possibility that ravens can use olfactory cues to find food.