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Spectroscopic Evidence for Self-Organization of N-Iodoacetylamphotericin B in Crystalline and Amorphous Phases.
MedLine Citation:
PMID:  23030378     Owner:  NLM     Status:  Publisher    
In this paper, we propose a new way of thinking about molecular self-organization of the antibiotic amphotericin B (AmB) by examination its N-iodoacetyl derivative (AmB-I). This choice was dictated by the simplicity of AmB-I crystallization as compared to pure AmB. The studies focus on spectroscopic investigations of the monocrystal and the amorphous state of AmB-I. The results of vibrational, FTIR, and Raman spectroscopy show differences between the crystalline and amorphous forms, in particular for bands attributed to C=O (1700-1730 cm-1) and C-C-H groups, as well as C=C-C (ca. 1010 cm-1) stretching vibrations. The process of crystallization is identified by strong differences in the intensities and locations of these characteristic bands. For the AmB-I crystals, the carbonyl band is shifted toward lower frequencies as a result of intensified hydrogen bonding in the crystalline form. Detailed analysis indicates that bands in the region characteristc for the C=C-C bending distortion in the chromophore are particularly intense for AmB-I in the crystalline form as compared to the intensity of this band in the amorphous state. These findings are corroborated by the results of fluorescence spectroscopy. We observe a much faster decay of the emission for the AmB-I monocrystal as compared to the DMSO solution of AmB-I. Interestingly, the fluorescence decay in the amorphous form requires three decay times for simulating the observed behavior, two of these decay constants are sufficient for estimating the decay measured for the AmB-I crystals. The proof of the molecular organization of AmB-I molecules is obtained from polarization-resolved fluorescence spectroscopy on a single AmB-I crystal. Strong anisotropy of the emission intensity correlates with the axes of the crystal providing insight into actual alingment of the molecules in the AmB-I crystals. These findings related to molecular organization in AmB-I crystals are crucial for understanding toxicity mechanisms of the clinicaly used drug, amphotericin B.
Mariusz Gagoś; Daniel Michal Kaminski; Marta Arczewska; Bartosz Krajnik; Sebastian Mackowski
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-3
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  -     ISSN:  1520-5215     ISO Abbreviation:  J Phys Chem A     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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