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A cytochrome c derivative from which iron is removed has been prepared and characterized. Several lines of evidence indicate that native and porphyrin cytochrome c have similar conformations: they have similar elution characteristics on Sephadex gel chromatography; in both proteins the tryptophan fluorescence is quenched and the pK values of protonation of the porphyrin are identical. Porphyrin cytochrome c does not substitute for native cytochrome c in either the oxidase reaction or in restoring electron transport in cytochrome-c-depleted mitochondria. It does however competitively inhibit native cytochrome c in these reactions, the Ki for inhibition being larger than the Km for reaction. The absorption and emission spectra, and the polarized excitation spectrum of the porphyrin cytochrome c are characteristic of free base porphyrin. The absence of fluorescence quenching of porphyrin cytochrome c when the protein is bound to cytochrome oxidase suggests that heme to heme distance between these proteins is larger than 0.5 to 0.9 nm depending upon orientation. Binding of the porphyrin cytochrome c to phospholipids or to mitochondria increases the fluorescence polarization of a positively polarized absorption band, which indicates that the bound form of the protein does not rotate freely within the time scale of relaxation from the excited state. [ABSTRACT FROM AUTHOR]

1. The interaction between aspartate aminotransferase and dicarboxylates of various chain lengths and geometries has been studied from pH 6.5 to 8.5 by circular dichroism (CD) and absorption spectroscopy. Liganding causes protonation of the pyridoxal phosphate-enzyme Schiff's base complex; the consequent changes in optical properties ΔAλ., ACDλ at the coenzyme maxima (λ = 363 or 430 nm) are analysed for binding constants and the degree of perturbation of the coenzyme protonic dissociation constant, pKa. 2. Aliphate dicarboxylates follow linear binding functions for all optical parameters; in contrast, m and p-phthalates follow non-linear binding functions for both ΔAλ and ΔCDλ, implying that successive phthalate ligands bind with decreasing affinity. The ratio ΔCDλ : ΔAλ is effectively constant for a given ligand and the characteristic values for aromatic ligands indicate a changed environment for the coenzyme. 3. Inspection of the non-linear process for phthalates suggests that initially, binding occurs with high affinity, but with characteristically small effects on pKa. It is inferred that aliphatic and aromatic dicarboxylates bind at different subsites in the active site region, perturbing the coenzyme pKa by an indirect protein-mediated mechanism. 4. Non-linearity of binding could derive from multiple binding to an individual subunit. Alternatively, different single sites may exist on adjacent subunits of the dimer, implying nonequivalence between otherwise identical subunits, expressed in properties involving groups close to the active site. [ABSTRACT FROM AUTHOR]

To show the occurrence of cytochrome c-1 in ϱ- petite mutants of Saccharomyces cerevisiae, in which its presence was questioned, low-temperature absorption spectra of various ϱ+ or ϱ- strains have been compared. Some of these strains carry nuclear mutations producing different types of cytochrome deficiencies, thus lowering the spectral interferences on cytochrome c1 and making easier its observation. The comparison was made with whole cells and with mitochondrial preparations. All the ϱ- mutants examined present a shoulder or a peak at a wavelength corresponding to cytochrome c1 in the ϱ+ strains. This absorption band at 552 nm in ϱ- mutants was further identified by isolating a cytochrome with an α absorption maximum at this wavelength. The low-temperature absorption spectrum of this cytochrome was compared to low-temperature absorption spectra of cytochrome c1 isolated from a wild-type strain, and of cytochrome c and cytochrome b2. It is similar, if not identical, to the spectrum of the wild-type cytochrome c1, and quite distinct of that of the other cytochromes. The cytochrome c1 content, in the various ϱ+ and ϱ- strains examined, is estimated with the help of a calculation procedure taking into account the spectral cross interferences of the cytochromes. In the absorption spectra of the ϱ- strains, a shoulder is recorded at about 557-558.5 nm. The nature of this shoulder is discussed. [ABSTRACT FROM AUTHOR]

The effect of azide on optical absorption and electron paramagnetic resonance (EPR) spectra of pig-plasma benzylamine oxidase has been examined and correlated with the effect of azide on the catalytic activity of the enzyme. A strong reversible interaction between azide and copper in benzylamine oxidase, corresponding to complex-formation with a dissociation constant less than 0.2 mM, was detected by EPR techniques. This interaction is competitive with the EPR-detectable binding of cuprizone to copper in the enzyme, but is not affected by reactions involving the active-site pyridoxal phosphate and has no evident effect on enzyme activity. A weaker reversible interaction between azide and protein-bound copper, corresponding to complex formation with a dissociation constant of 40 mM, was detected spectrophotometrically and by EPR techniques. An absorption band centered at 390 nm is associated with the latter complex, the apparent stability of which was found to be unaffected by a 20-fold variation of the oxygen concentration as well as by reduction of the enzyme with substrate. Azide acts as an uncompetitive inhibitor of benzylamine oxidase with an inhibition constant close to 40 mM. 100 mM azide has essentially no effect on the reactivity of the active-site pyridoxal phosphate towards phenylhydrazine or benzylamine. It is concluded that formation of the enzyme · azide complex exhibiting the 390 nm absorption band precludes reoxidation of the substrate-reduced form of the enzyme, indicating that at least one of the two copper ions in benzylamine oxidase may have a direct catalytic function in relation to the reoxidation process. [ABSTRACT FROM AUTHOR]

Low-temperature (77°K) fluorescence and absorption spectra have been determined for whole cells and photosystem I particles of Anacystis nidulans grown in iron-supplied or iron-deficient inorganic media. Iron deficiency induces a decrease of F720 relative to F685 and F695 in the fluorescence spectra of both whole cells and photosystem I particles. This change is correlated to a reduction of preferentially the long wavelength absorbing fraction of chlorophyll a. The relative fluorescence intensity at 755 nm is increased by iron deficiency. No significant effects of culture-age are found in the ratio between the three fluorescence bands (F685 : F695: F720) of iron-supplied A. nidulans. [ABSTRACT FROM AUTHOR]

The spectroscopically different phycocyanins present in the type strain of Hemiselmis virescens, Millport 64, and in a second strain of this cryptophytan species, Plymouth 157, have been purified and compared. They are similar in native molecular weight and in subunit structure, both containing α and β subunits with molecular weights of approximately 10 000 and 19 000 respectively. However, they do not have the same chromophore composition. Both subunits of the phycocyanin of Plymouth 157 contain two bilins, with absorption maxima at 600 and 660 nm, respectively. Only the β subunit of Millport 64 carries these chromophores; its α subunit bears another chromophore, with absorption maxima at 368 and 694 nm. The spectroscopic differences between the two native phycocyanins can be entirely accounted for by their differing chromophore compositions. The phycocyanin of Millport 64 is the only biliprotein so far described which contains three chemically different chromophores. [ABSTRACT FROM AUTHOR]

A new bacteriochlorophyll has been isolated by thin layer chromatography from all strains of the brown-colored Chlorobiaceae Chlorobium phaeobacteroides and Chlorobium phaeovibrioides. The new bacteriochlorophyll e -like the bacteriochlorophylls c and d-represents the major amount of bacteriochlorophyll in the cells in addition to small amounts of bacteriochlorophyll a. Bacteriochlorophyll e can be differentiated from the bacteriochlorophylls c and d by its absorption maxima in aceton and its different R-value in the thin layer chromatogram. The structure of the new bacteriochlorophyll e has been elucidated on the basis of mass spectra, H- and C-NMR-spectra, the UV/VIS-spectrum as well as IR-, ORD-, and CD-spectra. The new bacteriochlorophyll has the same relationship to bacteriochlorophyll c as chlorophyll b from green plants to chlorophyll a; therefore, bacteriochlorophyll e represents the first formyl-substituted chlorophyll from bacteria. Similar to the bacteriochlorophylls c and d, the new bacteriochlorophyll e consists of a mixture of at least three homologues which differ from each other by different substituents on the pyrrol rings II and III. [ABSTRACT FROM AUTHOR]

In water-methanol solutions, chlorophyll a forms aggregates absorbing at 745 ± 10 nm or at 710 ± 10 nm. In all cases, chlorophyll also gives a form with no absorption at wavelengths between 350 and 1000 nm, which is considered as an important aggregate of chlorophyll molecules (sieve effect). It is assumed that, in the immediate environment of the chlorophyll a molecules, the water/methanol ratio is the determining factor of the type of aggregate obtained and that water and chlorophyll compete for the “aggregation sites” of chlorophyll. [ABSTRACT FROM AUTHOR]

From an aqueous extract of the fruit of the tropical plant Thaumatococcus daniellii Benth, two sweet-tasting basic proteins, here named thaumatin I and thaumatin II, were isolated by ultrafiltration, gel filtraration on Sephadex G-50 and ion-exchange chromatography on SE-Sephadex C-25, using a sodium chloride concentration gradient. The proteinaceous character of the two sweet-tasting compounds was proven by the characteristic ultraviolet absorption spectrum, the presence of almost 100% polypeptide material as determined by the biuret method, the yiel of 100% amino acids on hydrolysis with hydrochlorid acid, the positive reaction with amido black colouring agent (as used in the analysis of the fractions by polyacrylamide gel and starch gel electrophoresis) and by the disappearance of the sweet taste of the compounds after incubation with trypsin. The basic character of the two proteins appears from their isoelectric points of almost 12, as estimated by starch gel electrophoresis at different pH values, and from the precipitation of the proteins at pH 12. The molecules of thaumatin I and II are very similar as shown from their amino acid compositions, which are practically equal; they also have the same N-terminal amino acid alanine and molecular weights of 21000 ± 600 and 20400 ± 600, respectivety (calculated from ultracentrifugal data). The proteins lose their sweetness on heating on splitting of the disulphide bridges in the molecule and at pH values below 2.5. Thaumatin I and II have an intensely sweet taste, the degree of sweetness being about 1600 times higher than that of sucrose on a weight basis or 105 times on a molar basis. The threshold values are near 10-4% or 48 nM. [ABSTRACT FROM AUTHOR]

1. The extra cellular ratio [lactate]/[pyruvate] is used as a means to poise the cytosolic NADH/NAD+ system. This is achieved by stepwise changes of [lactate]/[pyruvate] in the perfusate in an open system. Fluorescence and absorbance at NADH-specific wavelengths is recorded simultaneously with single or dual wavelength methods. Fluorescence excitation and absorbance difference spectra are obtained with the help of an instrument computer. The readout is calibrated by infusion of internal standards, permitting an estimation of the enhancement of quantum yield of NADH-specific fluorescence. 2. Mathematical treatment on the basis of the mass action law permits extrapolation to fully reduced and fully oxidized cytosolic bound NADH. In addition, the apparent equilibrium constant for bound NADH/NAD+ and lactate/pyruvate is obtained (0.022 to 0.071), corresponding to a midpoint potential of bound NADH of -260 to -265 mV. Accordingly, the ratio of dissociation constants, KNAD+/KNADH, relevant for the cytosolic binding sites, is 200-700. Cytosolic NADH-binding capacity is estimated to be around 80 nol/G liver wet weight. Under anorexic conditions at [lactate]/[pyruvate] of 10 in the perfusate. the ratio of contents of cytosolic bound NADH/free NADH is 100. 3. The existence of near-equilibrium conditions in the system is suggested by measurement of net H+ transport coupled to lactate import, as well as by determination of an intracellular dependent indicator metabolite couple, α-glycerophosphate/dihydroxyacetone phosphate. Problems regarding the validity of tissue contents of lactate/pyruvate as indicator for the cytosolic NADH/NAD+ potential are discussed. [ABSTRACT FROM AUTHOR]

Poly(s²C) · poly (I) complex formation (where s²C=2-thiocytidylate) was shown by spectrophotometrio titration, absorption-difference spectroscopy and hydroxyl-ion titration. The absorption temperature profile of the complex does not display a transition between 10 and 100 °C. Cooperative melting with a transition midpoint at 77 °C was observed only after destabilization by 30% ethylene glycol. A stabilizing effects of s²CMP residues in helices is further shown by the observation that 25% s²CMP in poly (C3,s²C) · poly (I) significantly increases the thermal stability compared to poly(C) · poly (I). The ultraviolet absorption spectrum, first derivative absorption spectrum and circular dichroism spectrum suggest, a weak n-π* transition at 320 nm in poly (s²C) · poly (I). Unlike other nucleoside diphosphates the polymerization of s²CDP by polynucleotide phosphorylase from Escherichia coli occurred with pronounced lag phase which disappeared after the addition of oligonucleotide primers. [ABSTRACT FROM AUTHOR]

A method has been developed for isolating and purifying peroxidase from hog intestinal mucosa. The enzyme exhibits an absorbance ratio A417 nm/A280 nm of 0.906. Studies on the homogeneity of intestinal peroxidase by electrophoresis on polyacrylamide gel and cellulose acetate strips showed its high degree of purification; the enzyme showed a single band at pH 8.45 with the cathodic mobility. Intestinal peroxidase is a haemoprotein. Its absorption spectrum, as well as that of its derivatives (CN-peroxidase, reduced peroxidase, CN-reduced peroxidase and pyridine haemochromogen) is of the same type as the spectrum of lactoperoxidase and its corresponding derivatives. Kinetic studies on the reaction of intestinal peroxidase with hydrogen peroxide and guaiacol showed that this haemoprotein has the properties of true peroxidase (donor: H2O2 oxidoreductase). The k1 value was determined as 5.9 × 106 M-1 × sec-1, and Km (H2O2) was 260 µM. Optimum pH of the studied peroxidase was in the range pH 7.5-8. Intestinal peroxidase, with respect to deamination and decarboxylation of amino acids, does not resemble the myeloperoxidase. [ABSTRACT FROM AUTHOR]

The nerve growth factor, purified from adult mouse submaxillary gland was analyzed for amino acid composition, isoelectric point and ultraviolet absorption spectrum. 1. The amino acid analysis showed the presence of ten-half cystine residues per mole of the nerve growth factor. Reagents for free sulfhydryl groups, such as 5,5-dithio-bis-(2-nitrobezoic) acid, p-hydroxy-mercury benzoate and iodoacetamide did not react with the protein even in presence of 8 M urea or 6 M guanidine · HCl; this suggests that all of the half-cystine residues are present in the nerve growth factor molecule in the oxidized form. From the amino acid composition the weight average of nitrogen was estimated as 17.62% and the partial specific volume was calculated as 0.716 ml per g. 2. The ultraviolet absorption spectrum at pH 5.0 showed a maximum in the 280-282 nm region and a second peak at 289 nm; the latter may indicate that the tryptophanyl residues present in the molecule are rather exposed. The ultraviolet spectrum did not change in presence of 8 M urea. 3. The isoelectric point, determined by the electrofocusing technique, was 9.30. This value explains the poor solubility observed for the nerve growth factor at neutral and alkaline pH and it is in agreement with the experimental observation that pH 5.0 is more indicated for the recovery and maintenance of the nerve growth factor activity during the course of the purification. [ABSTRACT FROM AUTHOR]

If no NADPH is available for reduction, fatty acid biosynthesis is blocked at the stage of the acetoacetyl-acyl carrier protein intermediate. In this case highly purified fatty acid synthetase from baker's yeast catalyzes, in a derailment reaction, the formation of triacetic acid lactone from acetyl- and malonyl-CoA. The identity, of the product was shown by the enzymatic incorporation of radioactivity from [1-14acetyl-CoA and from recrystallization to constant. specific radioactivity. In paper chromatography, thin layer chromatography, and ionophoresis both the chemically synthesized triacetic acid lactone and the enzymatically formed compound migrated with the same RF-values and electrophoretic mobility. By an oxidation with chromic acid according to the procedure of Kuhn-Roth it could be demonstrated that the radioactivity of [1-14C]acetyl-CoA is incorporated only into the C-6 position of triacetic acid lactone. Free triaceti acid and tetraacetic acid lactone do not seem to be formed by fatty acid synthetase. The ratio of the malonyl-CoA utilization for the synthesis of palmitoyl- and stearoyl-CoA to that for the synthesis of triacetic acid lactone was found to be about 90:1. The significance, of these findings is discussed. A chemical mechanism for the formation of triacetic acid lactone by fatty acid. synthetase is proposed. [ABSTRACT FROM AUTHOR]

When ferric myoglobin reacts with alkyl sulphates, its absorption spectrum changes into one characteristic of a haemichrome or parahaematin. The reaction equilibrium was studied over a range of protein concentrations using dodecyl sulphate and other alkyl sulphates with different chain lengths. The results obtained from spectrophotometric measurements and equilibrium dialysis experiments are not in agreement with those of other authors who. from an anal sis of spectral changes only, supported the hypothesis of an all-or-none type of reaction whereby 18 detergent. anions were bound to one molecule of ferric myoglobin. From the results we conclude that the first stage of the association of dodecyl sulphate to ferric myoglobin at pH 8.0 involves the binding of one molecule of detergent without alteration of the myoglobin absorption characteristics. In the second phase a further 3 or 4 molecules of dodecyl sulphate become associated. This causes the ferric myoglobin to be converted into its ferric myochrome, which exhibits the characteristic haemichrome absorption spectrum. The binding of additional dodecyl sulphate molecules to the myochrome then proceeds in numerous discrete steps, so that a great number of complexes occur simultaneously in the reaction medium. The experimental evidence indicates that the ferric myoglobin retains its native configuration in these complexes, provided the number of bound dodecyl sulphate anions does not exceed 50. The association compounds can be described as low-spin coordination complexes, in which a second imidazole originating from histidine E7, occupies the sixth coordination site of the iron atom. [ABSTRACT FROM AUTHOR]

The quantized action spectrum of photosynthesis for Skeletonema costatum was obtained from values of photosynthetic 14CO2 uptake at various wavelengths of light isolated with a diffraction grating monochromator. The quantized action spectrum of photosynthesis exhibited maxima at wavelengths similar to maxima in the absorption spectrum, in vivo, of a suspension of S. costatum cells. While the 14CO2 technique will provide an accurate action spectrum of photosynthesis for diatoms, a large number of samples is required in order to minimize sampling error. [ABSTRACT FROM AUTHOR]

Growth of anacystis nidulans in wavelengths of light predominantly absorbed by chlorophyll a causes dramatic lowering of the chlorophyll content with only small changes in phycocyanin and carotenoids. Steady-state growth under red photographic safe lamps produces cells with &frac14 of the chlorophyll content of cells grown under low intensities of white (tungsten) illumination. Pigment analyses permit resolution of in vivo absorption spectra into spectra of the component pigments and also the fractional absorption vs wavelenth. Even in normally pigmented cells physocyanin is the major collector of light quanta for photosynthesis. The observed pigment control is viewed as a special case of intensity control which has chromatic character by virtue of the presence of two different pigment systems liked to the two light reactions of photosynthesis. [ABSTRACT FROM AUTHOR]

Chlorella pyrenoidosa has been cultivated in radiation of wavelengths between 690-975 nm for several months. Absorption spectra and action spectra of photosynthesis have been determined for far red and "white" light grown cultures. In vivo spectrophotometric analyses and action spectra showed that far red grown Chlorella adapted to the extreme light conditions by an increase both in absorption and photosynthesis above 700 nm. It is proposed that som of the in vivo normal chlorophyll a forms were converted to a far red absorbing chlorophyll a form, giving the far red exposed suspension an increased photosynthetic activity between 700-740 nm. The analyses of far red grown Chlorella have also shown an increased photosynthesis in the blue part of the spectrum, presumably due to a decrease in photosynthetically inactive carotenoid content. By culturing Chlorella in a "white" light gradient between 0.5 × 104 and 3.7 × 104 erg cm-2 s-1, it has been demonstrated that light intensity did not influence pigment ratios between 500-750 nm. In the blue part, however, high light levels caused increased absorption because of increased carotenoid content. Some ecological aspects of this far red effect have also been discussed. [ABSTRACT FROM AUTHOR]

Experiments were carried out with viable and nonviable rice seeds to detect the nature of germination inhibitors. An abscisic acid like factor is present in nonviable seeds but absent in viable ones. The main source of the factor is the embryo although measurable amounts are also obtained from the husk; it is not found in the endosperm however. Interaction with GA3 and IAA suggests that both the rice seed inhibitor and abscisic acid are antagonistic to GA3 and partially reversed the IAA induced growth. The similarity of the UV absorption spectra of the inhibitor and abscisic acid also proves its presence in nonviable seeds. The inhibitor suppresses the α-amylase activity both in intact and excised seeds in the same way as abscisic acid but the suppression is partially overcome with higher concentrations of GA3. [ABSTRACT FROM AUTHOR]

Absorption spectrum of Rhodospirillum rubrum pigment complexes in basic solvents. - The adsorption and aggregation of bacteriochlorophyll are studied in various polar solvents, at different concentrations. It is shown that 3 absorption bands exist in these conditions, duplicating 3 of the absorption bands found in vivo: the 772 nm, the 830 nm and the 890 nm-bands. The 800 nm-band cannot be formed in vitro. The relations between the respective concentrations of the 3 states of bacteriochlorophyll found in vitro are calculated and discussed. [ABSTRACT FROM AUTHOR]

The action spectrum of photosynthetic O2-production was determined with chloroplast suspensions and while leaves. Owing to a dominating influence of light scattering the action spectrum shows a much more uniform absorption of the incident light than would be expected from the absorption spectrum in direct light (0° deviation). The comparatively strong photosynthesis in green is probably further aided by the light reaction between cytochrome f and chlorophyll in which also the cytochromes act as pigments. The whole region 400 to about 900 nm is photosynthetically active with an obvious tendency to linear relation between the intensity of incident radiation and photosynthetic O2 production, certain deviations hereby caused by specific absorption or activation. The results illustrate the participation of carotenoids in the primary energy conversion of photons to activated electrons and the role of at least two light reactions in the photosynthetic cycle. The reducing power of illuminated β-carotene was demonstrated in-vitro in its effect on ferredoxin. The steady state situation of pigments and enzymes is discussed. [ABSTRACT FROM AUTHOR]

The article presents information on photostructural reactions in chloroplasts. It is a well known fact that suspensions of mitochondria, chloroplasts and microorganisms show absorption spectra which al higher concentrations deviate from those of the extracted pigments. Examples of this effect of the turbidity were given in a previous communication dealing with yeast suspensions in various degrees of dilution. The characteristic effect of turbid solutions is scattering of the ingoing light beam or rather a combination of reflection and refraction at and in the particles.

Photoreactivation in both growth and motility of the green alga Platymonas subcordiformis was demonstrated. It was shown that the growth and the motility were correlated in this respect. When irradiated in the far ultraviolet region between 223 and 300 mμ two types of inactivations occurred. One type was the immediate reduction in the per cent of cells in motion (immediate immobilization). The action spectrum of this followed the absorption curve of proteins. The other type, which was recorded after one week, gave an action spectrum which followed the absorption spectrum of deoxyribonucleic acid (DNA). At wave lengths where the absorption of DNA is insignificant (223 and 238 mμ) the immobilization of the cells was autoreversible, to complete recovery in the light at wavelengths between 500 and 800 mμ which did not affect photoreactivation, and to 60 per cent in the dark. It is concluded that the immediate immobilization is caused by destruction of proteins including the enzymes, and that these were re-synthesized during anabolism when the DNA synthesis was not damaged. The action spectrum of photoreactivation showed great resemblance to a flavoprotein absorption curve. It is concluded that a flavoprotein is involved in photoreactivation of the motility, and most probably in the growth of Platymonas. [ABSTRACT FROM AUTHOR]

The absorption spectrum of the R-phycoerythrin from Ceramium rubrum is not only due to the chromophore, but to interactions between the chromophore and the protein. Evidence is presented to indicate that disulfide bonds, sulfhydryl group and hydrogen bonds are involved in these interactions. [ABSTRACT FROM AUTHOR]

The action spectra of positive and negative phototaxis in Platymonas show that the same photoreceptive pigment is involved in these two reaction types. In the far ultraviolet the algae are extremely sensitive to 220 mμ radiation. A minimum is observed at 255 mμ and a maximum at 275 mμ. This part of the action spectrum curve corresponds to the absorption spectrum of a protein which contains aromatic amino acids. In the near ultraviolet maximum occurred at 335 mμ, and in the visible region a small maximum at 405, a shoulder at 450, and a more prominent maximum at 495 mμ. The action spectrum curves in the near ultraviolet and the visible region correspond closely to the absorption characteristics of certain carotenoids. It is concluded that a carotenoprotein is the photoreceptive pigment complex in photic orientation. [ABSTRACT FROM AUTHOR]

1. Action spectra of topo-phototaxis in algae have been obtained by two methods: a) The algae were balanced for movements between two opposing beams, one reference beam which was kept constant in wave-length and intensity, and one exciting beam which was altered in wave-length and adjusted in intensity until the cells .swam toward neither light source. The pholotactic effectiveness of different wave-lengths was thus obtained. b) A spectrum having an intensity gradient was projected on one side of a vessel containing the algae, the other side was illuminated with light uniform in wave-length and intensity. Under these conditions the algae will collect on the side of the vessel where the spectrum is more effective than the uniform reference beam (positive phototaxis), and the action spectrum was obtained by measuring (be energy and wave-length along the boundary of collection. 2. The precision of the measurements was analyzed. 3. Action spectra of phototaxis have been measured for five species of Volvocales; for the gametes of two species of Ulva; and for three Dino-phyceae. 4. The Volvocales all have action spectra of phototaxis with a maximum at 493 mμ and with a small shoulder around 435 mμ. The action spectra of both species of Ulva-gametes have a maximum at 485 mμ and a shoulder around 435 mμ. Two of the Dinophyceae, Goniaulax catenella and Peridinium trochoideum, have action spectra with a maximum at 475 mμ the third, Prorocentrum micans, at 570 mμ. 5. Absorption spectra of living Volvocales and the Dinophyceae were measured. These spectra did not reveal any features indicating the presence of pigments corresponding to the action spectra of phototaxis. 6. Pigment analysis of Peridinium trochoideum and Prorocentrum micans showed that the same major fat-soluble pigments were present in both these species. 7. The action spectra of positive and negative phototaxis were identical for the same species in the Volvocales. Some observations strongly indicate that this was true for the Dinophyceae also. 8. Some of the theories about the function of the stigma in phototaxis are discussed. It is concluded that the directing mechanism in phototaxis consists of two parts, one of which is a light absorber located near the flagellar base. In order lo act in phototaxis, a shading organ is required with the ability to reduce by at least 10 per cent the light in the spectra! region where the light sensitive pigment absorbs. The stigma in colored forms, when present, is assumed to act only as an auxiliary body which on some occasions will improve (he precision of the movement. 9. The different action spectra have been analyzed and when the experimental errors and the screening effect of pigments within the cells are taken into consideration, it is concluded that at least two, possibly three, different pigments are involved in the phototaxis of the algae examined by us: a) the same pigment is assumed to be involved in the Volvocales and the Ulva-gametes; b) possibly (his same pigment is also involved in the phototaxis of Goniaulax catenella and Peridinium trochoideum; c) definitely different from these is the pigment involved in the phototaxis of Prorocentrum micans. 10. None of these pigment has been isolated and even their nature is unknown. [ABSTRACT FROM AUTHOR]

1. Avena seedlings exposed unilaterally to low dosages of ultraviolet show positive phototropic curvature which develops over the whole length of the plant and soon becomes mainly located in the base. Both the tip and the region around the node can detect the UV, and the sensitivity of these zones is approximately proportional to their relative growth rates. 2. The curvature is proportional to the logarithm of the applied energy and at wavelength 280 mμ it reaches a saturation value of 16 -20° at about 3000 ergs/cm2. 3. Plants which have been repeatedly decapitated become completely insensitive to the UV, but the sensitivity is largely restored by applying indoleacetic acid in agar blocks before exposure to UV. 4. The action spectrum of the curvature has been determined. It shows peaks at 280 and 297 mμ. The wavelengths absorbed by riboflavin are relatively ineffective. 5. The action spectrum for the photoinactivation of pure indoleacetic acid bas been determined under comparable conditions. It resembles exactly the absorption spectrum of this substance in solution. 6. It is tentatively suggested that the UV curvatures may be due to a light-sensitive, growth-controlling chemical compound of IAA, in which the absorption spectrum is slightly modified and shifted about 12 mμ towards longer wavelengths. [ABSTRACT FROM AUTHOR]

The action spectra were determined with a high intensity light source on 11 patients (including 4 persistent light reactors) known to be photosensitive to bithionol and halogenated salicylanilides. Maximum photosensitivity observed on patch tests containing the sensitizer was in the range of 360 nm. but no reaction occurred above 420 nm. The persistent light reactors had a considerably lowered sunburn MED below 330 nm. compared with control groups. The absorption spectra of the sensitizers was determined in dimethyl formamide arid in 95% ethanol at various pH. The halogenated salicylanilides gave a maximum absorption at 282 nm. in an acid pH, but in a basic pH above 8, when phenolic ionization occurs, a second absorption peak at 360 nm is found. Maximum fluorescence was achieved by excitation in the region of 360 nm. If the concentration of the sensitizer is equal (1%) then the order of decreasing photosensitizing ability of the tested substances was tetrachiorosalicylanilide (TCSA), bithionol. 4',5-dibromosalicylanillde (DBS) and 3,4'5-tribromosalicylanilide (TBS). Guinea-pigs could be sensitized with TCSA within one week using combined long U.V. (320-420 nm) and sunburn irradiation, but no sensitivity occurred with irradiation for 16 weeks using only long U.V. Patch tests on sensitized patients to photodecomposition products of TBS and DBS were negative. The possible mechanisms in the production of the persistent light reactors are discussed. [ABSTRACT FROM AUTHOR]

This article informs that the mechanism of phototoxicity seems to depend on the binding of the drug or of its metabolic products to components of the skin cells, the absorption spectrum of the drugs or its products, and the intensity and spectrum of the light to which the skin is exposed. If the agent binds to the cell membrane exposure to light causes damage to the membrane with leakage of cytoplasm. Where the agent concentrates in the lysosomes, light exposure causes lysosomal rupture and cell death.

An attempt has been made to establish the physical law which governs the equilibrium distribution of vat dyes between a reducing solution and cotton fibers. A relatively simple relationship gives a good approximation and also provides the means of a first approximation prediction of the effect of a second dye on the equilibrium uptake of the first. The theoretical and experimental approaches are presented and the predicted results compared with observed ones. [ABSTRACT FROM AUTHOR]

Spectrophotometric absorption measurements of colored solutions can be related to CIE Colorinietry. The area of an absorption curve is measured with a tristimulus intergrator and used to define the strength of the dye. The tristiinulus values are reduced to co-ordinates that locate the dye at a specific place on a color diagram. These two physical constants (strength and hue) are used to match aye mixtures by graphical methods or by titration. [ABSTRACT FROM AUTHOR]

The bromine atom in an o-bromo-o'-hydroxyazo dye has been found to react with wool in the presence of copper sulfate. Several reactive dyes of this type for wool have been prepared. The extent of reaction with the fiber has been studied. These dyes do not react with silk or nylon. The lightfastness of the dyeings on wool and nylon has been studied and found to be poor. [ABSTRACT FROM PUBLISHER]

The absorption spectra of some sunscreens have been measured and the transmission through them of wavelengths of 2900Å-5000Å have been calculated using concentrations of them customary in ointments. The least transmission was found with aesculin, followed by salol, pyriben-zamine, para-aminobenzoic acid, tannic acid, sulphanilamide, antipyrine, nicotinic acid and, resorcin, in order of increasing transmission. [ABSTRACT FROM AUTHOR]