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101.
Abstract— Irradiation with ultraviolet B (UVB, 290–320 nm) causes a systemic immunosuppression of cell-mediated immunity. The question of whether UV immunosuppression modulates the course of infectious diseases is important becauseUVB levels in sunlight are sufficient to predict significant UV-induced immunosuppression at most latitudes. We have investigated the effect of immunosuppressive doses of UVB on the disease caused by the helminth parasite Schistosoma mansoni. C57BL/6 mice were irradiated once or three times weekly over 60–80 days with UV from a bank of FS40 sunlamps. Each UV treatment consisted of an immunosuppressive UV dose, as determined by suppression of contact hypersensitivity to trinitrochlorobenzene, corresponding to about 15–30 min of noonday tropical sunlight exposure under ideal clear sky conditions. Cumulative UV doses were between 80 and 170 kJ/m2. Worm and egg burdens, liver granuloma diameters and liver fibrosis showed minimal changes(> 20%) compared with parameters in unirradiated animals. Ultraviolet irradiation (a total of 55 kJ/m2 administered in six treatments) did not impair the resistance to rechallenge conferred by vaccination with 60 Co-irradiated cercariae. We have thus observed a dichotomy between UV immunosuppression and both disease and vaccination in this helminth infection, in contrast to the effects of UVB shown in other infectious diseases. 相似文献
102.
Abstract—High resolution resonance Raman spectra of rhodopsin. isorhodopsin and photostationary state mixtures containing a high percentage of bathorhodopsin arc presented. New spectral features are detected which were not obsei-ved in lower resolution studies by other workers. All of the hands in the photostationary state spcctra arc assigned based on pure rhodopsin and isorhodopsin resonance Raman results and alterations in the photostationary state mixture. The spectral features in these spectra are invariant from 20 to 150K indicating that retinal and protein structural alteration, consistent with a model of excitation proposed by Lewis, occurs in steady-state spectra even at 20 K. In addition, the relative intensity of certain features in the photostationary state spectra are altered upon D2O suspension. One explanation for these alterations is that the contributions of various intcrmediates to the photostationary state mixture are changed when membrane fragments are suspended in D2O. 相似文献
103.
The efficiency of fluorescence resonance energy transfer (FRET) between two chromophores positioned at opposite ends of DNA base pair domains has been investigated. The base pair domain serves as a helical scaffold which defines both the distance between chromophores and the dihedral angle between their electronic transition dipole moments, each incremental base pair increasing the distance and stepping the dihedral angle. Fluorescence quantum yields and lifetimes have been determined for both the donor and acceptor chromophores. The experimental data are found to be in excellent accord with an oriented dipole model, rather than with the averaged dipole model conventionally assumed for FRET. 相似文献
104.
The selection and quality of hops is a major determinant in beer flavour. Brewers acknowledge that distinctive characteristics of different hop varieties can be traced to the composition of their essential oils. The difficulty in characterising complex mixtures such as hop oil using 1-D chromatography is that many compounds co-elute. With the introduction of comprehensive multidimensional capillary gas chromatography (GC x GC), there is a tremendous improvement in the separation power or peak capacity. Recent work using GC x GC with flame ionisation detection has suggested that there may be over 1,000 compounds in hop oil. This work describes the use of GC x GC combined with TOFMS detection (Leco Pegasus 4D instrument) to analyse Target hop oil. The TOFMS spectral acquisition rate of 60 Hz provided sufficient spectra per peak (2-D peak base width of 0.1-0.2 s) for identification (119 components were identified with 45 previously unreported compounds). When analysing results, an advantage of GC x GC coupled to TOFMS is that 2-D chromatograms can be viewed for individual masses that are characteristic of particular functional groups. This allows the analyst to view the various homologous series of compounds although in certain cases coelution may still be present as shown by the esters with mass 75. 相似文献
105.
J A Lewis D C Lommen W D Raddatz J W Dolan L R Snyder I Molnar 《Journal of chromatography. A》1992,592(1-2):183-195
Computer simulation software (DryLab I/mp) is described for predicting high-performance liquid chromatographic separation as a function of changes in mobile phase pH. Three experimental runs with pH (only) varied are used to derive values of pKa plus capacity factors (k') for the ionized and non-ionized form of each ionizable solute. Various tests of the experimental data then allow classification of each solute as acidic, basic, neutral (including strong or weak acids or bases) and amphoteric. Experimental data are reported for the separation of several substituted anilines as a function of pH and solvent composition (%B). Experimental requirements for the accurate prediction of separation (ca. +/- 2-4% in alpha) as a function of pH are discussed. The reliability of the software is demonstrated for three different samples: mixtures of (a) substituted benzoic acids, (b) substituted anilines and (c) catecholamine-related compounds. 相似文献
106.
107.
Larry N. Lewis 《Journal of organometallic chemistry》1982,234(3):355-365
The photoacoustic spectrum (PAS) was measured in the near IR region (1000 to 2600 nm) for organic compounds (C6H6, C6D6, C7H8, and C6H12) and organometallic compounds (Cp2Fe, Cp2Fe2(CO)4, Cp4Fe4(CO)4, Cp4Fe4S4, C6H6Cr(CO)3, CpCo(C4Ph4) and CpCo(CO)2). Band assignments were made by comparison to the infrared spectra. The bands were assigned as the CH overtone stretch and combinations of CH and other IR fundamentals. These bands provide fingerprint spectra for these compounds. 相似文献
108.
Lewis FD 《Photochemistry and photobiology》2005,81(1):65-72
Synthetic DNA conjugates in which one or both ends of a short duplex is capped by a stilbene chromophore have been prepared and characterized crystallographically. Selective excitation of the chromophore can be used to initiate electron transfer processes in which a nucleobase serves as either an electron donor or an electron acceptor. These processes include hole- and electron injection and hole migration. The dynamics of these processes and its dependence on distance, driving force, and base sequence have been investigated by means of femtosecond time-resolved spectroscopy. Duplexes with identical chromophores at both ends have been used to study both the dynamics of electron transfer processes and exciton coupling between the two chromophores by means of circular dichroism spectroscopy. Duplexes with different chromophores can also be used to study distance dependence of both electron transfer and exciton coupling. 相似文献
109.
A high-performance liquid affinity chromatographic method for the purification of serum immunoglobulin A (IgA) using a jacalin column is described. The automated procedure takes about 2 with minimal manipulation. The yields of the isolated IgA and of its IgG and IgM contamination were studied by enzyme-linked immunosorbent assay (ELISA) of 30 sera. Purity was assured by immunoelectrophoresis. The ratio of IgA1 to total IgA was unchanged after purification, as verified by ELISA. The results showed that greater than 90% IgA could be recovered with less than 0.5% total IgG and greater than 2.0% total IgM remaining in the fractions containing purified IgA. 相似文献
110.
David F. V. Lewis 《Journal of computational chemistry》1989,10(2):145-151
Results of molecular orbital (MO) calculations by the complete neglect of differential overlap (CNDO /2) method on 50 small molecules are reported. The summation of calculated atomic polarizabilities are equated with molecular polarizabilities, and these are compared with experimentally determined values. It is found that there is very good agreement between calculated and experimental molecular polarizability. This provides a reliable method for the determination of molecular polarizabilities for compounds for which experimental values are not known. The relationship between log P and polarizability is discussed and analyzed in terms of contributions from electronic components to the partitioning energy. 相似文献