SERGEI VINOGRADOV, Ph.D.

Associate Professor of Biochemistry and Biophysics

Location: 901C Stellar-Chance Building
Tel: (215) 898-6382
Fax: (215) 573-3787
Email: vinograd@mail.med.upenn.edu

Ph.D. Moscow State University (1995)

DESCRIPTION OF RESEARCH INTERESTS

Our research revolves around functional molecular systems related to biological objects by function or by application. We use methods of synthetic organic chemistry to rationally design and construct molecules with preferred degree of active site encapsulation, predefined photophysical properties and tunable energy and electron transfer pathways. Our special area of interest is development of advanced probes for optical microscopy and imaging. In particular, we are developing methods for optical imaging of oxygen in biological tissues using phosphorescence quenching. We design and use dendritically protected phosphorescent probes in combination with instrumentation and algorithms developed in our laboratory to perform in vivo oxygen imaging experiments, addressing various biological problems through collaborations with scientists from Penn Medical School and other universities.

Two areas of organic chemistry are recurrent in our research: porphyrins and dendrimers. We study a new class of near-infra red absorbing p-extended porphyrins (tetrabenzoporphyrins, tetranaphthaloporphyrins etc), for which we have devised a practical synthetic approach. We look into the photophysics, including non-linear optical properties, acid/base properties and electrochemistry of these new porphyrins, addressing various structure-property relationships in the extended porphyrin family.

Dendrimers provide a convenient and straightforward way for macromolecular encapsulation of optically active sites. Dendritic cages control access of small molecules to the encapsulated cores, providing an effective way of selective sensing of small molecules in biological systems. Dendrimers with porphyrin cores also bear many similarities with heme containing proteins. We use photophysical methods to probe diffusion of small molecules inside dendrimers, serving as models of natural macromolecular scaffolds.

Currently, we are currently developing two new technologies for biological oxygen imaging: oxygen tomography by phosphorescence lifetime and multiphoton microscopy of oxygen. Both techniques are relevant to research in cancer and peripheral vascular disease, while oxygen microscopy is also expected to have an impact in ophthalmology and neuroscience. Optical probes for oxygen tomography and microscopy, theory, algorithms and instrumentation are being addressed in our group.

RECENT REPRESENTATIVE PUBLICATIONS:

1. Finikova, O.S., Troxler, T., Senes, A., DeGrado, W.F., Hochstrasser, R.M., Vinogradov, S.A. (2007) Tuning energy and electron transfer rates in Pt-tetrabenzoporphyrin-rhodamine assemblies for two-photon imaging of oxygen. J. Phys. Chem. A 111:6977-6990.
2. Apreleva, S.V., Wilson, D.F., Vinogradov, S.A. (2006) Tomographic imaging of oxygen by phosphorescence lifetime. Applied Optics 45:8547-8559 (cover image).
3. Finikova, O. S., Cheprakov, A. V., Vinogradov S. A. (2005) Synthesis and luminescence of soluble meso-unsubstituted tetrabenzo- and tetranaphtho[2,3]porphyrins. J. Org. Chem. 70:9562-9572.
4. Brinas, R.P., T. Troxler, R.M. Hochstrasser, S.A. Vinogradov (2005) Phosphorescent oxygen sensor with dendritic protection and two-photon absorbing antenna. J. Am. Chem. Soc. 127:11851-11862.
5. Percec, V., Dulcey, A. E., Balagurusamy, V.S.K., Miura, Y., Smidrkal, J., Peterca, M., Nummelin, S., Edlund, U., Hudson, S.D., Heiney, P.A., Duan, H., Magonov, S.N., Vinogradov S.A. (2004) Self-assembling amphiphilic dendritic dipeptides that mimic helical protein pores. Nature 430:764-768; appeared in C&EN News, in "Chemistry Highlights 2004" (Dec. 20, 2004)
6. Finikova, O.S., Galkin, A.S., Rozhkov, V.V., Cordero, M., Hagerhall, C., Vinogradov, S.A. (2003) Porphyrin- and tetrabenzoporphyrin-dendrimers: tunable membrane-impermeable fluorescent pH nanosensors. J. Am. Chem. Soc. 125:4882-4893.