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Dive into the research topics where Stephen A. Waschuk is active.

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Featured researches published by Stephen A. Waschuk.


Science | 2006

Coherent Control of Retinal Isomerization in Bacteriorhodopsin

Valentyn I. Prokhorenko; Andrea M. Nagy; Stephen A. Waschuk; Leonid S. Brown; Robert R. Birge; R. J. Dwayne Miller

Optical control of the primary step of photoisomerization of the retinal molecule in bacteriorhodopsin from the all-trans to the 13-cis state was demonstrated under weak field conditions (where only 1 of 300 retinal molecules absorbs a photon during the excitation cycle) that are relevant to understanding biological processes. By modulating the phases and amplitudes of the spectral components in the photoexcitation pulse, we showed that the absolute quantity of 13-cis retinal formed upon excitation can be enhanced or suppressed by ±20% of the yield observed using a short transform-limited pulse having the same actinic energy. The shaped pulses were shown to be phase-sensitive at intensities too low to access different higher electronic states, and so these pulses apparently steer the isomerization through constructive and destructive interference effects, a mechanism supported by observed signatures of vibrational coherence. These results show that the wave properties of matter can be observed and even manipulated in a system as large and complex as a protein.


Biochimica et Biophysica Acta | 2008

Screening and characterization of proteorhodopsin color-tuning mutations in Escherichia coli with endogenous retinal synthesis.

So Young Kim; Stephen A. Waschuk; Leonid S. Brown; Kwang-Hwan Jung

Proteorhodopsin is photoactive 7-transmembrane protein, which uses all-trans retinal as a chromophore. Proteorhodopsin subfamilies are spectrally tuned in accordance with the depth of habitat of the host organisms, numerous species of marine picoplankton. We try to find residues critical for the spectral tuning through the use of random PCR mutagenesis and endogenous retinal biosynthesis. We obtained 16 isolates with changed color by screening in Escherichia coli with internal retinal biosynthesis system containing genes for beta-carotene biosynthesis and retinal synthase. Some isolates contained multiple substitutions, which could be separated to give 20 single mutations influencing the spectral properties. The color-changing residues are distributed through the protein except for the helix A, and about a half of the mutations is localized on the helices C and D, implying their importance for color tuning. In the pumping form of the pigment, absorption maxima in 8 mutants are red-shifted and in 12 mutants are blue-shifted compared to the wild-type. The results of flash-photolysis showed that most of the low pumping activity mutants possess slower rates of M decay and O decay. These results suggest that the color-tuning residues are not restricted to the retinal binding pocket, in accord with a recent evolutionary analysis.


Proceedings of the National Academy of Sciences of the United States of America | 2005

Leptosphaeria rhodopsin: Bacteriorhodopsin-like proton pump from a eukaryote

Stephen A. Waschuk; Arandi G. Bezerra; Lichi Shi; Leonid S. Brown


Biochemistry | 2004

FTIR spectroscopy of the K photointermediate of Neurospora rhodopsin: structural changes of the retinal, protein, and water molecules after photoisomerization.

Yuji Furutani; Arandi G. Bezerra; Stephen A. Waschuk; Masayo Sumii; Leonid S. Brown; Hideki Kandori


Biochemistry | 2005

Strongly hydrogen-bonded water molecule present near the retinal chromophore of Leptosphaeria rhodopsin, the bacteriorhodopsin-like proton pump from a eukaryote.

Masayo Sumii; Yuji Furutani; Stephen A. Waschuk; Leonid S. Brown; Hideki Kandori


Science | 2007

Response to Comment on "Coherent Control of Retinal Isomerization in Bacteriorhodopsin"

Valentyn I. Prokhorenko; Andrea M. Nagy; Stephen A. Waschuk; Leonid S. Brown; Robert R. Birge; R. J. Dwayne Miller


Biochemistry | 2006

Conformational coupling between the cytoplasmic carboxylic acid and the retinal in a fungal light-driven proton pump.

Yuji Furutani; Masayo Sumii; Ying Fan; Lichi Shi; Stephen A. Waschuk; Leonid S. Brown; Hideki Kandori


Seibutsu Butsuri | 2006

2P308 Asp to Glu substitution in the cytoplasmic channel dramatically affects the photocycle of bacteriorhodopsin-like protein from a Eucaryote(41. Proton and ion pumping,Poster Session,Abstract,Meeting Program of EABS & BSJ 2006)

Yuji Furutani; Masayo Sumii; Ying Fan; Lichi Shi; Stephen A. Waschuk; Leonid S. Brown; Hideki Kandori


生物物理 | 2005

1P272 プロトンポンプ活性をもった真核生物ロドプシンLeptosphaeria Rhodopsinの構造解析(光生物 A) 視覚・光受容))

昌代 住井; 祐詞 古谷; Stephen A. Waschuk; Leonid S. Brown; 秀樹 神取


Seibutsu Butsuri | 2005

1P272 Structural analysis of Leptosphaeria rhodopsin, bacteriorhodopsin-like proton pump protein from a eucaryote

Masayo Sumii; Yuji Furutani; Stephen A. Waschuk; Leonid S. Brown; Hideki Kandori

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Yuji Furutani

Graduate University for Advanced Studies

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Hideki Kandori

University of California

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Ying Fan

University of Guelph

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Hideki Kandori

University of California

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