Ultrafast Vibrational Spectroscopy

In order to design efficient light harvesting materials it is extremely important to understand the structural motifs in biological photo-machinery e.g. in the photosynthetic reaction centers and photoenzymes. Coherent motions in form of specific vibrational modes have been proposed to play a key role in such photoactive systems. Consequently tracing transient changes in atomic positions and elucidating reactive nuclear coordinates within a polyatomic system becomes imperative. Our group will be using a newly developed time-resolved vibrational technique, femtosecond stimulated Raman spectroscopy (FSRS) with the aim of probing a vast range of dynamic events occurring on the excited electronic states such as photo-triggered isomerization, electron transfer and proton transfer events both in the bulk and at interfaces. Armed by the excellent spectral (~5 cm^-1) and temporal (< 50 fs) resolution of FSRS, we plan to reveal the critical skeletal modes that drive all these basic reactions at the ultrafast limit.

 Coding Self-repair in Photomaterials

In the quest for renewable energy, developing an inexpensive light harvesting technology will be incumbent upon us within the next few decades as we move away from the finite natural resources of coal, gas and petroleum. In this context designing new materials for either solar cells or photocatalytic processes with a higher photochemical or photon-conversion efficiencies is crucial. One key feature in all these materials will be the need to be robust and fault-tolerant. We will explore new ideas on incorporation of self-repair within a designed molecular photocatalyst and hope to create “generalized structure rules” which will be necessary in all future molecular materials.

J. Dasgupta, A.M. Tyryshkin, S.V. Baranov and G.C. Dismukes,

Bicarbonate participates in the assembly of the tetra-Mn Cluster in Photosystem II: pH dependence of Mn³⁺ EPR signal,

Appl. Magn. Reson. (2010) 37, 137–150

R. Frontiera, J. Dasgupta and R.A. Mathies,

Femtosecond Raman structural studies of photoinduced electron transfer at a dye/semiconductor interface;

 J. . Am. Chem. Soc. (2009) 131, 15630-2

K. Spillane, J. Dasgupta, J. C. Lagarias and R. A. Mathies,

Homogeneity of Phytochrome Cph1 Vibronic Absorption Revealed by Resonance Raman Intensity Analysis,

J. Am. Chem. Soc. (2009) 131, 13946–13948

S. Shim, J. Dasgupta and R.A. Mathies,

Femtosecond Time-Resolved Stimulated Raman Reveals the Birth of the J and K Intermediates in Bacteriorhodopsin’s Photocycle,

J. Am. Chem. Soc. (2009) 131, 7592–7597

J. Dasgupta, R. Frontiera, K. Taylor, J.C. Lagarias, R.A. Mathies,

Ultrafast Excited State Isomerization in Phytochrome Revealed by Femtosecond Stimulated Raman Spectroscopy,

Proc. Natl. Acad. Sci USA (2009) 106, 1784-1789.

J. Dasgupta, G.M. Ananyev and G.C. Dismukes,

Photoassembly of the Water-Oxidizing Complex in Photosystem II,

Coord. Chem. Rev. (2008) 252(3-4), 347-360.

J. Dasgupta, A.M. Tyryshkin and G.C. Dismukes,

ESEEM Spectroscopy Reveals Carbonate and N-donor Protein Ligand Binding to Mn²⁺ in the Photoassembly Reaction of the Mn₄Ca cluster in Photosystem II,

Angew. Chem. Int. Ed. (2007), 46, 8028-8031

A.M. Tyryshkin, R. Watt, S.V. Baranov, J. Dasgupta, M. Hendrich and G.C. Dismukes,

Ca²⁺ Directs the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water Oxidizing Complex:  Formation of a Ligand Bridge to Mn³⁺ via Deprotonation,

Biochemistry (2006), 45, 12876-12889. 

J. Dasgupta, A.M. Tyryshkin, Yu.N. Kozlov, V.V. Klimov and G.C. Dismukes,

Carbonate complexation with Mn²⁺ in Aqueous Phase: Redox Behavior and Ligand Binding Modes by Electrochemistry and EPR,

J. Phys. Chem. B (2006), 110, 5099-5111.

G.C. Dismukes, V.V. Klimov, S.V. Baranov, Yu. N. Kozlov, J. Dasgupta, and A.M. Tyryshkin,

The Origin of Atmospheric Oxygen on Earth: The Innovation of Oxygenic Photosynthesis,

Proc. Natl. Acad. Sci. USA (2001), 98, 2170–2175.