After many years of advances, the School goes on its first graduate student retreat

At the beginning of November, many of the School’s graduate students and faculty spent a scientifically stimulating and enjoyable weekend at Unicoi state park and lodge.

Humboldt Award for Ken Brown

School of Chemistry and Biochemistry Professor Ken Brown will partner with colleagues in Germany to help develop molecular quantum logic spectroscopy.

Colorful and Dynamic Workshops

School of Chemistry and Biochemistry Professor Rigoberto Hernandez and Research Scientist Kyril Solntsev are organizing unique workshops in the mountains.

School of Chemistry and Biochemistry to Host Charles L. Liotta Symposium

This year marks Regents Professor Emeritus Charles Liotta’s 50th at Georgia Tech, and the celebration is on.

Seminars & Events

Dr. Katarzyna Adamala - Massachusetts Institute of Technology
Special Seminar - Thursday, January 8, 2015 - 4:00pm - MoSE 3201A
Meeting - Thursday, January 15, 2015 - 11:00am - MoSE 2100F
Meeting - Tuesday, January 20, 2015 - 11:00am - MoSE 3201A
Prof. Julie S. Biteen - University of Michigan
Colloquium - Thursday, January 29, 2015 - 4:00pm - MoSE G011

Featured Research

Article Title
Research Authors
Pagba, C.V.., Chi, SH.., Perry, J.., Barry, B..
Journal of Physical Chemistry B (2015), Vol. DOI: 10.1021/jp510171z, ASAP
Miscellaneous Details
This research was funded by NSF CLP 12-13350 (B.A.B.).

In proteins, proton-coupled electron transfer (PCET) can involve the transient oxidation and reduction of the aromatic amino acid tyrosine. Due to the short life time of tyrosyl radical intermediates, transient absorption spectroscopy provides an important tool in deciphering electron-transfer mechanisms. In this report, the photoionization of solution tyrosine and tyrosinate was investigated using transient, picosecond absorption spectroscopy. The results were compared to data acquired from a tyrosine-containing β-hairpin peptide. This maquette, peptide A, is an 18-mer that exhibits π–π interaction between tyrosine (Y5) and histidine (H14). Y5 and H14 carry out an orthogonal PCET reaction when Y5 is oxidized in the mid-pH range. Photolysis of all samples (280 nm, instrument response: 360 fs) generated a solvated electron signal within 3 ps. A signal from the S1 state and a 410 nm signal from the neutral tyrosyl radical were also formed in 3 ps. Fits to S1 and tyrosyl radical decay profiles revealed biphasic kinetics with time constants of 10–50 and 400–1300 ps. The PCET reaction at pH 9 was associated with a significant decrease in the rate of tyrosyl radical and S1 decay compared to electron transfer (ET) alone (pH 11). This pH dependence was observed both in solution and peptide samples. The pH 9 reaction may occur with a sequential electron-transfer, proton-transfer (ETPT) mechanism. Alternatively, the pH 9 reaction may occur by coupled proton and electron transfer (CPET). CPET would be associated with a reorganization energy larger than that of the pH 11 reaction. Significantly, the decay kinetics of S1 and the tyrosyl radical were accelerated in peptide A compared to solution samples at both pH values. These data suggest either an increase in electronic coupling or a specific, sequence-dependent interaction, which facilitates ET and PCET in the β hairpin.

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