Abstract：
:The proton channels of the bacteriorhodopsin (BR) proton pump contain bound water molecules. The channels connect the purple membrane surfaces with the protonated retinal Schiff base at the membrane center. Films of purple membrane equilibrated at low relative humidity display a shift of the 570 nm retinal absorbance maximum to 528 nm, with most of the change occurring below 15% relative humidity. Purple membrane films were dehydrated to defined humidities between about 50 and 4.5% and examined by Fourier transform infrared difference spectroscopy. In spectra of dehydrated-minus-hydrated purple membrane, troughs are observed at 3645 and 3550 cm-1, and peaks are observed at 3665 and 3500 cm-1. We attribute these changes to water dissociation from the proton uptake channel and the resulting changes in hydrogen bonding of water that remains bound. Also, in the carboxylic acid spectral region, a trough was observed at 1742 cm-1 and a peak at 1737 cm-1. The magnitude of the trough to peak difference between 1737 and 1742 cm-1 correlates linearly with the extent of the 528 nm pigment. This suggests that a carboxylic acid group or groups is undergoing a change in environment as a result of dehydration, and that this change is linked to the appearance of the 528 nm pigment. Dehydration difference spectra with BR mutants D96N and D115N show that the 1737-1742 cm-1 change is due to Asp 96 and Asp 115. A possible mechanism is suggested that links dissociation of water in the proton uptake channel to the environmental change at the Schiff base site.
journal_name
Photochem Photobioljournal_title
Photochemistry and photobiologyauthors
Renthal R,Gracia N,Regalado Rdoi
10.1562/0031-8655(2000)072<0714:wacgei>2.0.co;2subject
Has Abstractpub_date
2000-11-01 00:00:00pages
714-8issue
5eissn
0031-8655issn
1751-1097journal_volume
72pub_type
杂志文章abstract：:Work in the past 8 years, particularly in the past 1-2 years, has greatly expanded our understanding of the mechanisms by which ultraviolet irradiation stimulates melanogenesis in the skin. A direct effect of UV photons on DNA results in up-regulation of the gene for tyrosinase, the rate-limiting enzyme in melanin syn...
journal_title：Photochemistry and photobiology
pub_type： 杂志文章,评审
doi：10.1111/j.1751-1097.1996.tb02988.x
更新日期：1996-01-01 00:00:00
abstract：:DNA UVB dosimeters, consisting of minidots of dried bacteriophage DNA placed on a UV-transparent polymer film, were analyzed by polymerase chain reactions (PCR). Ultraviolet-B dosimetry obtained with amplification of phage lambda DNA of segments of 1.08 kilobase pairs (kbp) and 2.24 kbp was compared with that obtained...
journal_title：Photochemistry and photobiology
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journal_title：Photochemistry and photobiology
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journal_title：Photochemistry and photobiology
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journal_title：Photochemistry and photobiology
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pub_type： 杂志文章
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更新日期：1993-04-01 00:00:00
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journal_title：Photochemistry and photobiology
pub_type： 杂志文章
doi：
更新日期：1998-10-01 00:00:00
