Addition Absorption Research Articles

A comparison of native and synthetic mushroom melanins by fourier-transform infrared spectroscopy

The diffuse reflectance Fourier-transform infrared spectra of the spore of the cultivated mushroom, Agaricus bisporus, of the melanin isolated therefrom and of various synthetic melanins related to the native material were recorded. There were prepared from γ-glutaminyl-4-hydroxybenzene (GHB; the presumed precursor of melanin in this fungus) as well as from simple phenol analogues of GHB, through auto- or enzyme-mediated oxidation and with, or without, potential non-phenolic co-reactants. The spectrum of the spore is dominated by distinct IR absorptions due to melanin, chitin and protein, while the isolated pigment is characterized mainly by the melanin absorption band at 1600 cm −1, which can be attributed primarily to aromatic groups whose signal is enhanced by phenol functionalities and, to a lesser extent, by amido groups. In addition, pronounced alkyl and carbonyl absorption bands were observed, and there is evidence of extensive C O and C N bonding in the biopigment. The spectrum of the melanin made from GHB through enzyme catalysis (phenolase, EC 1.14.18.1/1.10.3.1.) most closely matched that of the biopigment. Use of 4-aminocatechol (AC) instead of GHB afforded a product which was similar to the native melanin, whereas the pigment obtained by air oxidation of 4-aminophenol (AP) was largely dissimilar. Cross-linking of the reacting phenol with protein was apparent in the melanin formed enzymatically from AC, but no evidence for such reactivity was present in the AP-derived melanin. Preformed chitin did not become incorporated into either synthetic melanin. The fungus does not synthesize melanin from AP, nor directly from GHB, but from AC in a proteinaceous environment represented in part by the phenol oxidase itself.

Biopharmaceutical aspects of anti-infective therapy at the extremes of age.

Optimal anti-infective therapy at the extremes of age can be supported by the development of appropriate dosage forms. With regard to neonates, infants and children an oral liquid formulation appears to be superior compared with standard formulations such as tablets and capsules, since individualized dosing by body weight or body surface area is more easily achieved. Reformulation of marketed dosage forms, such as crunched tablets or opened capsules, by the hospital pharmacist may result in stability and bioavailability problems and therapeutic failures may be the consequence. With regard to the elderly a reduction in dosing frequency and individualized dosing are important in order to increase compliance. A reduction of dosing frequency can be achieved by oral controlled-release dosage forms, which are designed to release the drug in small amounts at predefined rates. However, to permit ease of swallowing they require a relative small daily dose together with excipients. In addition absorption must occur throughout the entire gastrointestinal tract; this is not the case for several antibiotics. Various advantages and disadvantages of oral liquid and oral controlled-release dosage forms are discussed. In the development of an oral formulation, in addition to a standard tablet a variety of information, such as physico-chemical characteristics, pharmacokinetics and pharmacodynamics must be available. Physico-chemical disadvantages can largely be solved by advanced pharmaceutical concepts, such as the pro-drug approach, complex formation or coprecipitation, which are discussed. Using ciprofloxacin with its long lasting and extremely bitter taste as an example, the pharmaceutical development of an oral liquid formulation and the pharmacokinetic investigations in healthy volunteers are described.

Interference mechanisms of sodium chloride on zinc and cobalt in graphite furnace atomic absorption spectrometry using a dual cavity platform

The interferences of sodium chloride with the determination of a volatile (zinc) and a low volatility (cobalt) element by graphite furnace atomic absorption spectrometry (GFAAS) were examined. For various masses of the sodium chloride, the effects of pretreatment temperature and time, and heating rate on the atomization of the analyte were investigated using a specially designed dual cavity platform, which in principle allows the analyte and the interferent to vaporize from the separate cavities so that gas and condensed phase interferences can be distinguished to some extent. In addition, background and atomic absorption signals obtained in the pretreatment step provided very important information to clarify the interference mechanisms. In the presence of sodium chloride, formation of a highly volatile zinc chloride contributes mainly to the losses of zinc, especially during high pretreatment temperatures. The losses of zinc and cobalt can partly be attributed to the occlusion of the analytes in microcrystals of the interferent and some of these are thrown from the furnace without decomposing early in the atomization step or during the pretreatment step. In addition, expulsion of both analytes together with the violently expanding matrix gases seems to be a likely interference mechanism as well.

Low polarity ligands of sex hormone-binding globulin in pregnancy. Part II—Identification

Certain previously unrecognized ligands of SHBG of low polarity in pregnancy were identified. They include two weakly bound compounds: 5α-pregnane-3,20-dione and progesterone; and two strongly bound substances, 2-methoxyestrone and a new steroid, estradienolone (17β-hydroxy-1, 5-estradiene-3-one). The identification of the first three peaks was based on chromatographic elution patterns, binding characteristics and gas chromatography-mass spectrometry. The identification of the fourth peak, the new steroid, was based on similar kinds of evidence and, in addition, solubility characteristics and ultraviolet absorption spectrum.

IUE spectroscopy of U Cephei during the mass flow outburst of 1986 June

The interacting Algol-type binary U Cep underwent another of its irregularly occurring transient high-mass flow events during June 1986. For the first time, high-resolution ultraviolet spectroscopy of U Cep during such an event was possible. High-resolution spectra in the far-ultraviolet and near-ultraviolet were obtained with IUE. These spectra show that the ultraviolet continuum decreased by factors of 1.2 to 3.0 during the greatest activity. In addition, one or more narrow absorption components with radial velocities as high as -500 km/s appeared in association with a number of C, Si, Al, Fe, Zn, and Mg lines. The Mg II doublet developed a flat-bottomed appearance with a residual intensity of about 0.31 and a width of at least 800 km/s. These phenomena are interpreted in terms of high-velocity gas streams, mass loss from the system, and the formation of an optically thick equatorial bulge around the B star.

A general purpose XUV laser spectrometer: some applications to N 2, O 2 and CO 2

Coherent radiation is generated from 90 to 105 nm by frequency tripling the frequency-doubled output of a pulsed Nd: YG-pumped dye laser using a synchronized pulsed jet of various gases as the nonlinear medium. The XUV radiation is isolated by a pair of dichroic mirrors before interacting with a supersonically cooled gas target. Provisions have been made to measure the photoion yield as a function of wavelength using a time-of-flight mass spectrometer. In addition absorption by the target gas or fluorescence from the excited target and/or its fragments can be detected. Some applications are presented which illustrate the versatility of this XUV laser spectrometer involving 1+1 resonance-enhanced multiphoton ionization of N 2 and excitation of Rydberg states of O 2 and CO 2.

Picosecond spectroscopy of isolated membranes of the photosynthetic green sulfur bacterium Prosthecochloris aestuarii upon selective excitation of the primary electron donor

Picosecond excitation at 850 nm of isolated membranes of the photosynthetic green sulfur bacterium Prosthecochloris aestuarii, when the primary electron donor P-840 was in the oxidized state, caused the formation of excited states of bacteriochlorophyll (BChl) a in the antenna, but not those of other pigment molecules, as had been observed upon excitation at shorter wavelengths. When, however, P-840 was initially in the reduced state, the flashes produced in addition absorption changes that could be attributed to reaction center components. These changes included bleachings of the absorption bands of P-840 and of BChl c. The latter bleaching, caused by BChl c reduction, decayed in 700 ± 70 ps, due to electron transfer to the next electron acceptor, whereas the bleaching of the bands of P-840 did not reverse in the time region studied (up to 3 ns). Analysis of the absorbance changes appeared to indicate a 1:1 stoichiometry for P-840 oxidation and BChl c reduction. The primary charge separation occurred in less than 10 ps.

Pyrimidine 5′nucleotidase and several other red cell enzyme activities in β‐thalassaemia trait

The activity of 18 red blood cell (RBC) enzymes and reduced glutathione (GSH) content were measured in 70 normal subjects, in 50 heterozygous beta-thalassaemia carriers and in 50 non-thalassaemic patients with haemolytic anaemia and high reticulocyte counts. In addition, pyrimidine 5'nucleotidase (P5N) activity was also determined in 34 patients with hypochromic, microcytic, iron deficiency anaemia. beta-Thalassaemia trait was associated with an increase in almost all of the enzyme activities, except for 2,3-bisphosphoglycerate synthetase (BPGS) and glutathione reductase (GR) which were normal and for acetylcholinesterase (AChE) and P5N which were slightly and markedly decreased respectively. The increases in enzyme activities were similar to those observed in patients with non-thalassaemic reticulocytosis except for glyceraldehydephosphate dehydrogenase (GAPD), phosphoglyceratekinase (PGK), pyruvate kinase (PK), glutathione peroxidase (GPX) and adenylate kinase (AK) which were higher than in non-thalassaemic group of patients with increased number of reticulocytes. No correlation was found between the severity of P5N deficiency and the intensity of basophilic stippling which was present in 46 of 50 thalassaemic carriers here studied. In addition, GSH content and UV absorption spectra of deproteinized thalassaemic RBC extracts were also found to be normal. The present findings provide further information on the metabolic status of RBC in beta-thalassaemia trait and suggest a possible molecular explanation for the frequently observed basophilic stippling in this disease.

The effect of detergent treatment on methylene blue sensitized cytochrome b photoreduction in fractions from corn coleoptiles

AbstractIt was previously demonstrated that photoexcited methylene blue can act as electron donor in red light induced reduction of a particulate b‐type cytochrome in fraction from etiolated corn coleoptiles (Zea mays L. WF 9 × Bear 38). It was postulated that the same cytochrome as the one active in blue light photoprocesses was involved. This study describes the effect of detergents upon such red light induced reductions in corn coleoptile preparations fractionated after differential centrifugation into 9 KP, 21 KP and 50 KP (500–9000 g pellet, 9000–21,000 g pellet and 21,000–50,000 g pellet, spun for 20, 20, and 45 min, respectively). Both Triton X‐100 (more effective) and deoxycholate (less effective and somewhat destructive) could be used as solubilizers if concentrations above the critical micellar concentration were chosen. Tween 40 was ineffective and dodecyl sulphate affected the cytochrome so that it lost its accessibility to electrons from photoexcited methylene blue. The recovery, measured as the ratio between light induced absorbance change (LIAC) in the Soret region after and before solubilization, was highest in 9 KP (70%) and lower in 21 and 50 KP fractions (50% and 43% respectively). The band in the Soret region in light minus dark spectra had its peak at longer wavelengths compared to the dithionite reduced minus no addition absorption difference band, whether the sample was solubilized or not. Similar results were obtained when the material was separated on a discontinuous sucrose gradient (15/28/33/45% w/w sucrose). In such a separation, the distribution of LIAC between fractions (collected at the interfaces) was about the same after solubilization as before (solubilization brought about a slight shift towards heavier fractions). The ratios of LIAC to the dithionite reduced minus no addition absorbance difference decreased upon detergent treatment. The LIAC still had its peak at longer wavelengths compared to the peak obtained upon dithionite reduction.The usefulness of detergents in the purification of the particulate b‐type cytochrome is discussed.

Two photon excitation spectrum of benzene and benzene-d6 in the gas phase: Assignment of inducing modes by hot band analysis

The two-photon absorption spectrum for benzene-h6 and -d6 is reported and assigned, leading to the frequency assignment for hitherto unknown vibrations in the electronically excited state. In addition absorption has been measured from hot bands in the ground state. This latter technique has allowed us to make an unequivocal assignment of the vibrational modes responsible for inducing the otherwise forbidden two-photon process. The result is in disagreement with current theory, for this prototype two-photon spectrum in the gas phase.

Absorption of carbaryl from the lung and small intestine of the rat

To investigate the pulmonary and intestinal absorption of the insecticide carbaryl (1-naphthyl- N-methylcarbamate; Sevin), solutions of the compound (0.005–0.1 m m) were administered into the lungs or small intestine of anesthetized rats. After various times, the organs were removed and assayed for compound that remained. Percentage of the dose unabsorbed was plotted semilogarithmically against time, and absorption half-times ( t 1 2 ) were calculated from the resulting curves. Results indicated that carbaryl was absorbed from the lungs ( t 1 2 = 2.6 min ) 2.5 times faster than from the small intestine ( t 1 2 = 6.4 min ). In addition, pulmonary and intestinal absorption of the insecticide appeared to occur by a nonsaturable process such as diffusion, since the amount of compound absorbed per unit time was directly proportional to the administered concentration.

Some Effects of Cations and of Water Absorption on Intestinal Hexose, Glycine and Cation Absorption.

SummaryFourteen mMolar hexose or glycine plus 100 to 210 mMolar sodium or non-sodium salts were perfused through jejunal or Heal loops in non-anesthetized dogs. Net water movements changed in response to the chemical identity as well as to the osmolarity of the perfusate. In general, hexose and glycine absorption rates decreased as water absorption rates decreased. At given water absorption rates however, glucose and galactose absorption rates were lower when K or NH4 salts were substituted for Na salts. Fructose, sorbose and glycine absorption rates did not differ between sodium and non-sodium per-fusates. In a second series, .310 osmolar solutions containing varying proportions of NaCl and KC1, NaCl and NH4C1, or KC1 and NH4C1 were perfused. Cation absorption rates increased directly with the concentration of the same ion and with water absorption rates. In addition, NH4 and Na absorption rates decreased as (K) increased, Na and K absorption decreased as (NH4) increased, and NH4 absorption decreased as ...

Infrared Absorption and Photoconductivity in Irradiated Silicon

The effects of irradiation on the infrared absorption and photoconductivity in silicon are reported. The absorption near the intrinsic edge is increased and drops off more gradually toward longer wavelengths. Several absorption bands are introduced by neutron irradiation with peak absorptions at 1.8, 3.3, 3.9, 5.5, and 6.0 μ, respectively. The observation of each band depends upon the position of the Fermi level. The 1.8-μ band has also been studied for deuteron irradiated and electron irradiated silicon, and the 3.3-μ band has been observed in electron irradiated samples. The absorption bands arise from electronic excitations of various types of defects and associated photoconductivity has been observed for the 3.9-μ and 5.5-μ bands. In addition absorption bands have been observed at long wavelengths: 20.5, 27.0, and 30.1 μ, which are associated with lattice vibration. The significance of these results is discussed.