Specific solvation of chlorophyll b: A site-selection study at 5 K

✍ Scribed by Radka S. Vladkova; Koit H. Mauring; Indrek V. Renge

• Book ID: 103992963
• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 497 KB
• Volume: 3
• Category: Article
• ISSN: 1011-1344
• DOI: 10.1016/1011-1344(89)80018-1

✦ Synopsis

The site-selection fluorescence excitation spectra of chlorophyll b were recorded in three different types of polar solvent host at 5 K. The influence of specific solvation of chlorophyll b on the Si state vibrational modes active in these spectra was studied in the high frequency vibrational region above 1000 cm-i. The nucleophilic solvation of chlorophylls (i.e. one or two axial extra ligands at the central magnesium atom), unlike electrophilic interactions (hydrogen bonding), can be detected very successfully by the method used. The maximum down-shift of 20 -30 cm-' of the high characteristic vibrational frequencies in the C=C stretching region estimated under electronic excitation of chlorophyll b is comparable with the effect of magnesium biligation and is explained in terms of an expansion of the tetrapyrrolic macrocycle core of the molecule. The broad-band fluorescence spectra of chlorophyll b in the same frozen solutions recorded at different laser excitation wavelengths are also presented and discussed.