Richard Mathies

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Ever since the conversion of the 11-cis retinal chromophore to its all-trans form in rhodopsin was identified as the primary photochemical event in vision, experimentalists and theoreticians have tried to unravel the molecular details of this process. The high quantum yield of 0.65 (ref. 2), the production of the primary ground-state rhodopsin photoproduct(More)
The kinetics of the primary event in vision have been resolved with the use of femtosecond optical measurement techniques. The 11-cis retinal prosthetic group of rhodopsin is excited with a 35-femtosecond pump pulse at 500 nanometers, and the transient changes in absorption are measured between 450 and 580 nanometers with a 10-femtosecond probe pulse.(More)
Strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on Mars. Although organic molecules are often codeposited with terrestrial evaporitic minerals, there have been no systematic investigations of organic components in sulfate minerals. We report here the detection of organic material, including amino acids and(More)
Spectral tuning by visual pigments involves the modulation of the physical properties of the chromophore (11-cis-retinal) by amino acid side chains that compose the chromophore-binding pocket. We identified 12 amino acid residues in the human blue cone pigment that might induce the required green-to-blue opsin shift. The simultaneous substitution of nine of(More)
The complex between double-stranded DNA and ethidium homodimer (5,5'-diazadecamethylene)bis(3,8-diamino-6-phenylphenanthridini um) cation, formed at a ratio of 1 homodimer per 4 or 5 base pairs, is stable in agarose gels under the usual conditions for electrophoresis. This unusual stability allows formation of the complex before electrophoresis and then(More)
The orange carotenoid protein (OCP) serves as a sensor of light intensity and an effector of phycobilisome (PB)-associated photoprotection in cyanobacteria. Structurally, the OCP is composed of two distinct domains spanned by a single carotenoid chromophore. Functionally, in response to high light, the OCP converts from a dark-stable orange form, OCP(O), to(More)
The biological function of Glu-181 in the photoactivation process of rhodopsin is explored through spectroscopic studies of site-specific mutants. Preresonance Raman vibrational spectra of the unphotolyzed E181Q mutant are nearly identical to spectra of the native pigment, supporting the view that Glu-181 is uncharged (protonated) in the dark state. The pH(More)
Novel latching microfluidic valve structures are developed, characterized, and controlled independently using an on-chip pneumatic demultiplexer. These structures are based on pneumatic monolithic membrane valves and depend upon their normally-closed nature. Latching valves consisting of both three- and four-valve circuits are demonstrated. Vacuum or(More)
The second extracellular loop of rhodopsin folds back into the membrane-embedded domain of the receptor to form part of the binding pocket for the 11-cis-retinylidene chromophore. A carboxylic acid side chain from this loop, Glu181, points toward the center of the retinal polyene chain. We studied the role of Glu181 in bovine rhodopsin by characterizing a(More)
The analysis of the vibrational spectrum of the retinal chromophore in bacteriorhodopsin with isotopic derivatives provides a powerful "structural dictionary" for the translation of vibrational frequencies and intensities into structural information. Of importance for the proton-pumping mechanism is the unambiguous determination of the configuration about(More)