摘要:

A number of studies have demonstrated the dependence of both the fluorescence lifetimes and quantum yields of tyrosine in solution upon the nature of the solvent as well as upon the absence or the presence of air in the tyrosine solutions employed. Photobleaching of tyrosine in vacuum at pH 6.1 was found to be practically zero, whereas exposure of tyrosine to the full light of a Hglamp for 10 to 20 minutes gave rise to formation of non-fluorescing photoproducts(1). In addition, the phosphorescence lifetimes of tyrosine were determined as 2.7+−0.2 sect 2.7+0.2 sec. and < 1 sec in 1% ETOH in aqueous solution and at pH 6.1 and pH 13, respectively(l). The very long phosphorescence lifetimes are definitely responsible to a considerable extent as far as photobleaching is concerned. However, the participation of the excited singlet state cannot be ruled out. In a review, the fluorescence lifetimes of tyrosine in queous solutions were found to vary between 2.6 nsec to 3.6 nsec(2). On the other hand, the fluorescence quantum yields of tyrosine and various anologous compounds displayed a strong dependence upon the solvent. Such solvents used were water, n-butanol and p-dioxane. The following values offlwere obtained: For p-HO-C6H4-CH2COOH;fl=0.01, 0.22 and 0.34; for p-HO-C6H4-CH3;fl= 0.23, 0.39 and 0.45 and for p-HO-C6H4-CH2CN;fl=0.16, 0.34 and 0.34, respectively(3). Furthermore, the valueflof p-HO-C6H4-CH2CH(NH+3)C00−in aqueous solutions was found to be 0.21, where- as that of p-HO-C6H4-CH2CH(NH+3)COOH in similar solutions was 0.06. The fluorescence lifetime and quantum yield of phenol in Ethanol were found to be 4.7 nsec and 0.10, respectively(4).

ISSN:0038-7010    

DOI:10.1080/00387017408067243

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The formation of hydrogen bonded complexes and the protonation of tertiary amides was investigated by infrared spectrometry and nuclear magnetic resonance. The complexation of secondary amides was however the subject of more restricted work. The interaction of N-methylacetamide (NMA) with phenol1, with proton donor or proton acceptor solvents2or with kaolinite3brings about a perturbation of some vibrational modes of the amide. In this work, we have determined the complexation constants (K) and the frequency shifts of the 1VOHand 1vC˭Ovibrations of hydrogen bonded complexes formed between NMA and phenol derivatives. For PKavalues higher than 6, the absence i n the spectra of the a characteristic frequencies of the amidium ion, suggest that the complexes are in the normal form:

ISSN:0038-7010    

DOI:10.1080/00387017408067244

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A harmonic force field is developed for AlF3, and used to re-calculate the mean amplitudes of vibration and the Bastiansen-Morino shrinkage effect. A vibrational re-assignment of observed frequencies from literature is proposed for Al2F6. Harmonic force constants and mean amplitudes are reported also for this molecule.

ISSN:0038-7010    

DOI:10.1080/00387017408067245

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

In a previous paper1the infrared spectra of some chelates of the type N,N′-ethylenebis(acetylacetoneiminato)-metal(II) were reported and the vibrational assignments were made on a correlative basis and with the aid of the results of a normal coordinate treatment. In order to provide further data for a more reliable assignment of the vibrational spectra of this class of metal chelates an investigation was carried out on the infrared pleochroism of the single crystals of N,N′-ethylenebis(acetylacetoneiminato)-copper(II) (CuBae.1/2H20 in the following).

ISSN:0038-7010    

DOI:10.1080/00387017408067246

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Current concepts on the association of molecules by means of a hydrogen bond (H-bond) are based on donor-acceptor interactions1,2. It is assumed that this interaotion is accomplished in all the steps of proton movement from A to B in the reaction (1)

ISSN:0038-7010    

DOI:10.1080/00387017408067247

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Polarized Raman spectra of Cs3UO2F5in which the UO2F53−ion is in its statistical position have made it possible to assign definitely the Raman fundamental vibration modes as follows : v1(A′1) = 784, v2(A′1) = 423, v8(E′2) = 325, v8(E′2) = 219 and v10(E″1) = 259 cm−1.

ISSN:0038-7010    

DOI:10.1080/00387017408067248

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The influence of the degeneration of the resonant energy levels on the photon echo intensity is investigated.

ISSN:0038-7010    

DOI:10.1080/00387017408067249

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0038-7010    

DOI:10.1080/00387017408067242

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor