摘要:

AbstractThe invention and subsequent use of laser as a light source in Raman spectroscopy ignited a wide application of Raman spectroscopy to organic compounds, biological compounds, and to biological tissues. Raman spectroscopy is a vibrational spectroscopy; Raman frequency is related to the mode of various vibrations in a molecule.In this review article, the use of Raman spectroscopy on biological molecules done at A. T. Tu's laboratory from 1962 to 1998, until his retirement, is summarized. The first part of the article is on peptide backbone structure and the local environment of amino acid residue side chain in proteins, mainly on snake neurotoxins. The second and third parts are direct analyses of gallstones and kidney stones by Raman spectroscopy without extraction, separation, and tedious chemical analysis. The last part is about the use of Raman spectroscopy to determine the anomeric bond in hexapyranosyl compounds.

ISSN:0009-4536    

DOI:10.1002/jccs.200300001

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractAs the 21stcentury begins, consumers in all countries are accepting natural medicines to improve quality of life, maintain health, and treat chronic and age‐related diseases. Accordingly, scientists worldwide are increasingly interested in the discovery and development of new drugs from plant, marine, and other sources. Natural resources have become more attractive as potential sources of new medicines, especially to treat cancer and AIDS. Recent progress in these areas will be discussed with emphasis on the discovery and development of clinically useful compounds as well as candidates for clinical trials. Contributions in these areas from the authors' laboratory will also be include

ISSN:0009-4536    

DOI:10.1002/jccs.200300002

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe electrochemical reduction mechanism of five 4‐cyano‐3‐substituted sydnones was investigated at a hanging mercury drop electrode by cyclic, linear sweep and differential pulse voltammetric methods in Britton‐Robinson buffer (pH 1.68–11.76). The electrode kinetics of 4‐cyano‐3‐(p‐tolyl)sydnone were studied in protic and aprotic solvent containing different tetra‐alkylammonium salts supporting electro

ISSN:0009-4536    

DOI:10.1002/jccs.200300003

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractTime‐resolved thermal lensing (TRTL) techniques have been applied to resolve photophysical and thermodynamic parameters for various metastable species, of which the relaxation dynamics are dominated by the radiationless transition. Using 1H‐phenalen‐1‐one as a sensitizer, the lifetime (τΔ), absolute quantum yield (ΦΔ) and efficiency of generation (STΔ) of singlet molecular oxygen (1Δg) have been determined in various organic solvents. In particular, through the development of an ultrasensitive detecting system, TRTL studies on the relaxation dynamics of O2(1Δg) become feasible in aqueous solution. In another application, based on the TRTL technique in combination with the O2sensitization experiment, the T1‐S0energy gap of the proton‐transfer tautomer in 3‐hydroxyflavone, which is otherwise inaccessible due to the dominant radiationless deactivation, has been deduced to b

ISSN:0009-4536    

DOI:10.1002/jccs.200300004

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractTwo mononuclear manganese(III) and iron(III) complexes with substituted salicylaldimine ligands, [MnL(H2O)2]Cl·H2O (1) and [FeL(H2O)(Cl)]CH3CN (2) [H2L = N,N′‐(1,1‐cyclohexane)bis(3‐methoxysalicylaldimine)] were prepared and characterized. The X‐ray crystal structure shows that1and2centers are six‐coordinate with distorted octahedral geometry. In1, the hydrogen bonding of water molecules form a quasi one‐dimensional chain structure. The temperature dependence of magnetic susceptibility measurements for complexes of1and2was analyzed in terms of the zero‐field splitting (D) spin‐Hamiltonian formula withD= 2.0 cm−1for1andJ= 7.5 cm−1, andD= 0.01 cm−1for2, respectively. The complexes of1and2activate the epoxidation ofcis‐stilbene or α‐methylstyrene by NaOCl. With1the epoxides were produced in 75% yield withcis:trans= 12:88 fromcis‐stilbene and 82% from α‐methylstyrene, and with2the epoxides were produced in 43% withcis:trans= 30:70 fromcis‐s

ISSN:0009-4536    

DOI:10.1002/jccs.200300005

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractTreatment of benzo[b]cyclohepta[e][1,4]oxazines (4) with 1.2 equiv. of tris(2‐aminoethyl)amine (13) in methanol at 80 °C gave 1,4,12,15,18,26,31,39‐octaazapentacyclo[13.13.13.05,11.019,25.032,3]pentetraconta‐4,6,8,10,18,20,22,24,31,33,35,37‐dodecacenes (14), armed tropocoronands (15), and tropopodands (16). The structure of tristropocryptand14awas determined by the X‐ray diffract

ISSN:0009-4536    

DOI:10.1002/jccs.200300006

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA series of polydimethylsiloxane (PDMS)/polyhydrogenmethylsiloxane (PHMS)/polymethylphenylsiloxane (PMPS) random copolymers with different phenyl contents were synthesized in one step through triflic acid‐catalyzed ring‐opening polymerization of cyclic comonomers and characterized by GPC, IR and NMR. Sequential structures of the random copolymers were determined by29Si‐NMR spectroscopy. Thermal properties of these copolymers were studied by DSC and TGA. The effect of phenyl moiety on the thermal properties of the copolymers was discussed. The refractive index (nD) increased regularly with the introducing of phenyl‐functionality as e

ISSN:0009-4536    

DOI:10.1002/jccs.200300007

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractNanoclusters AgI have been prepared in the channels of SBA‐15 molecular sieve host, and the host‐guest nanocomposite materials were prepared by a heat diffusion method. The (SBA‐15)‐AgI host‐guest nanocomposites were characterized by powder X‐ray diffraction analysis, nitrogen adsorption‐desorption isotherms at 77 K, and solid‐state diffuse reflectance absorption spectra. The decrease in surface area, pore diameter, and pore volume showed the existence of silver iodide clusters in the channels of SBA‐15 host. X‐ray diffraction illustrates that the framework of the SBA‐15 remained in the host‐guest composites of (SBA‐15)‐AgI. As the guest loading decreases, a blue‐shift was observed in the diffuse reflectance spectra. This shows that the guest existed in the channels of SBA‐15 and a quantum confinement effect emerged. The photoluminescence (PL) spectra show that the PL at ∼2.38 eV, associated with the hydrogen‐related species, decreases substantially after the loading of AgI in SBA‐15. The decrease of the PL indicates the reduction of the hydrogen concentration on the pore surface of SBA‐15 after the loading of AgI guest. The intensity decrease of the self‐trapped exciton (STE) band at 2.76 eV also suggests a hindrance for generating the excitons upon

ISSN:0009-4536    

DOI:10.1002/jccs.200300008

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe solvolysis ofα‐tert‐butyl‐2‐naphthylmethyl, 9‐fluorenyl, and some 1‐aryl‐1‐tert‐butylmethyl tosylates (8–10) in a variety of solvents were studied. Both the single‐parameter Hammett‐Brown equation and the dual‐parameter Yukawa‐Tsuno equation showed linear correlations. The variation of ρ values was discussed. A newYxBnOTsscale was developed, and theYBnOTsscale was expanded. Solvent effects for a number of tosylates were examined. Excellent linear relationships observed from the single‐parameter Grunwald‐Winstein equation (Eqn. 2) for 9‐fluorenyl tosylate (10) led to the conclusion that the 9‐fluorenyl cation in the solvolysis transition state was unlikely antiaromatic. Anchimeric assistance i

ISSN:0009-4536    

DOI:10.1002/jccs.200300009

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA glass liner of a PTV injector packed with porous crab shell powder (50–100 mesh) was used to enrich the trace concentrations of sulfur components in natural gas, then the sulfur gases were thermally released according to a programmed temperature from the crab shell powder trap and re‐collected in a PLOT‐column head cooled with liquid nitrogen. The sulfur compounds were revolatilized and directly transferred to the system of PLOT‐column gas chromatography/flameless sulfur chemiluminescence detector for analysis. The characteristics of natural crab shell powder as an adsorbent have been presented. The sulfur gaseous compounds known to cause nuisance odors in natural gas were determined. The application of a porous crab shell powder trap for the analysis of sulfur compounds from gaseous samples has been proved to be

ISSN:0009-4536    

DOI:10.1002/jccs.200300010

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY