Linked Life Data

11272723

Source:http://linkedlifedata.com/resource/pubmed/id/11272723

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2001-3-1
pubmed:abstractText
The natural product hypericin was tested in recent years as a biological photosensitizer with a potential for viral and cellular photodamage. We thus studied extensively its spectroscopy and membrane partitioning. Absorption, fluorescence excitation and emission spectra of the sodium salt (HyNa) were measured in 36 protic and aprotic, polar and apolar, solvents. Electronic transition bands as well as vibrational progressions were identified. Aggregation in some nonpolar solvents and protonation in organic acids were demonstrated. Modeling solvatochromism was done by Lippert equation, by the ET(30) parameter and by the Taft multiparameter approach. In all cases, separation into protic and aprotic solvents gave much better fits to the models. 13C chemical shift data could also be correlated with solvent polarity. They correlated best with Lippert's delta f polarity measure, but tended to fall into two distinct solvent groups--each along different lines--corresponding to protic and aprotic media, respectively. This interesting phenomenon suggests that in the case of the charged and slightly water soluble HyNa, two mechanisms of solvation are involved, each resulting in its own line equation. In aprotic media, dipole-dipole interaction is the predominant solvation mechanism. In protic solvents, the most effective means of solvation is likely to be hydrogen bonding. When intercalated into the liposomal phospholipid bilayer, HyNa is oriented at an angle to the interface, thus experiencing a gradient of solvent polarities: a highly polar environment (similar to methanol) for C-2/5, suggesting that they lie not far from the interface; a moderately polar environment (similar to that of n-propanol) for C-6a/14a, which are somewhat deeper within the bilayer; and a more lipophilic environment (akin to n-hexanol) for C-10/11. The fluorescence excitation peak in liposomes also correlates with an aprotic medium of relatively high polarity, as might be excepted from a molecule in a shallow position in the bilayer.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0031-8655
pubmed:author
pubmed:issnType
Print
pubmed:volume
73
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
110-8
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Solvatochromic effects in the electronic absorption and nuclear magnetic resonance spectra of hypericin in organic solvents and in lipid bilayers.
pubmed:affiliation
Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't