Code: MOB	Time Slot/Poster Number: 10:30 - 11:00 am	Session: Resonance Raman of Biological Systems I
Modulation of the conformation of Cytochrome c Oxidase from Paracoccus denitrificans by active-site mutations
Denis Rousseau1; Hong Ji1; Tsuyoshi Egawa1; Tapan Das1; Anne Puustinen2; Marten Wikstrom2; Syun-Ru Yeh1
1Albert Einstein College, Bronx, NY; 2University of Helsinki, Helsinki, Finland
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Summary
The properties of mutants of cytochrome c oxidase from Paracoccus denitrificans (PdCcO) were investigated with resonance Raman spectroscopy. Based on the Fe-CO stretching modes and low frequency heme modes, two conformers (alpha- and beta-forms) were identified that are in equilibrium in the enzyme. We present a model in which the mutations destabilize the alpha-conformer, with respect to the beta-conformer, and raise the activation barrier for the inter-conversion between the two conformers. The accessibility of the two conformers may play a critical role in coupling the redox reaction to proton translocation during the catalytic cycle of the enzyme.

Code: MOB	Time Slot/Poster Number: 11:00 - 11:30 am	Session: Resonance Raman of Biological Systems I
High Protein Structural Flexibility Of A Truncated Hemoglobin From An Antarctic Cold-Adapted Bacterium
Barry D. Howes1; Daniela Giordano3; Leonardo Boechi2; Simona Mucciacciaro1; Maria Fittipaldi1; Darío A. Estrin2; Massimo Coletta4; Cinzia Verde3; Giulietta Smulevich1
1Università di Firenze, Sesto F.No (Fi), Italy; 2Universidad de Buenos Aires, Buenos Aires, Argentina; 3CNR, Naples, Italy; 4Università di Roma Tor Vergata, Rome, Italy
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Summary
Although many cold-adapted marine species have been studied, we still have limited knowledge about molecular adaptations at low temperatures. We present the first detailed spectroscopic characterization of hemoglobin from the cold-adapted Antarctic bacterium Pseudoalteromonas haloplanktis in its ferric state. This protein revealed unique features among Group II of 2/2 hemoglobins, being characterized by an aquo high spin and multiple hexacoordinated low spin forms. Both TyrCD1 and TyrB10 are proposed to be alternatively involved in heme low-spin hexa-coordination. The results indicate high protein structural flexibility, which is probably required for cellular functioning in extreme cold environments.

Code: MOB	Time Slot/Poster Number: 11:30 - 11:50 am	Session: Resonance Raman of Biological Systems I
Evaluation of Inter-subunit Interactions in Half-ligated Human Adulat Hemoglobin based on the Single Residue UVRR Spectra
Teizo Kitagawa1; Shigenori Nagatomo2; Masako Nagai3
1University of Hyogo, Ako, Japan; 2University of Tsukuba, Tsukuba, Japan; 3Hosei University, Koganei, Japan
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Summary
The single residue vibrational spectra of Trp and Tyr residues playing important roles in cooperative oxygen binding of human hemoglobin A were determined for the deoxy and CO-bound forms with UVRR spectroscopy. Trpβ37, Tyrα42 and Tyrα140 adopt two alternative states during ligand binding. The corresponding spectral changes were identified for the α2β2 tetramer but not for the isolated chains, and thus attributed exclusively to a quaternary structure change. The spectra of these residues in the half-ligated form were determined with ligand-, metal-, and valency-hybrid Hbs. The behaviors of Trp and Tyr were not synchronous against the concerted change model.

Code: MOB	Time Slot/Poster Number: 11:50 am - 12:10 pm	Session: Resonance Raman of Biological Systems I
Purines as Interrogators of Local Environment in Proteins and DNA
Sayan Mondal; Spriha Gogia; Namrata Jayanth; Mrinalini Puranik
National Centre for Biological Sciences, Bangalore, India
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Summary
We have characterized several natural purines that are substrates of nucleic acid binding proteins e.g., 8-oxoguanosine and aminopurines and their analogues . The ultraviolet resonance Raman spectra were supported by DFT calculations. Raman spectra show that 1-methyladenosine monophosphate in solution is pH dependent and undergoes a transition from the imino to amino form as pH is changed. Aminopurines are well known fluorescent analogues of adenine. The Raman spectra of aminopurines yield bands that are well separated from adenine and other natural nucleobases.

Code: MOB	Time Slot/Poster Number: 12:10 - 12:30 pm	Session: Resonance Raman of Biological Systems I
UV Resonance Raman-derived Initial Excited-state Structural Dynamics of Nucleobases, Nucleosides and Dinucleotides
Glen Loppnow
University of Alberta, Edmonton, Canada
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Summary
Nucleic acids are very good at removing excess energy resulting from photon absorption, although photochemistry can still occur, leading to cancer and other diseases. UV resonance Raman spectroscopy is a useful probe of the initial excited-state structural dynamics, an important step in photochemistry, for molecules which undergo ultrafast relaxation from the excited electronic state. This presentation will describe the results of UV resonance Raman spectroscopic measurment of nucleobases, nucleosides, and dinucleotides of a number of nucleic acid components, and the initial excited-state structural dynamics derived from those intensities. These results will be discussed in the context of nucleic acid photochemistry.