Biosurface Spectroscopy

Dr. V. Volkov

Properties of interfaces are of vital importance in our time and always will be as long as there shall be a rational motive to preserve life environment, to improve our well-being, and to increase resolving power in learning and understanding of nature, in general.

Phospholipid membrane plays a structural constituent role in a living cell. Besides it mediates a variety of biochemical cellular events. Being largely disordered and composed of bulky molecules, phospholipid membrane is the environment where infrared optical spectroscopy has a unique resolving power. Consequently, the research efforts concern the very nature of vibrational states and dynamics at phospholipid membrane interface. Till recently, I employed ultrafast two-dimensional χ^-3 spectroscopy tools and theoretical methods, like ab initio and classical molecular dynamic simulation. Accordingly, it was possible to map spectrally the complete set of diagonal resonances and cross-peaks characteristic to hydrated phospholipid membrane fragments.

V. Volkov, F. Nuti, R. Takaoka, Y., Chelli, A. M. Papini, R. Righini JACS 2006, 128, 9466.
V. Volkov, D. Jason Palmer, and Roberto Righini Phys. Rev. Lett. 2007, 99, 078302.
V. Volkov, R. Chelli, W. Zhuang, F. Nuti, Y. Takaoka, A. M. Papini, S. Mukamel and R. Righini Proc. Natl. Acad. Sci. USA 2007, 104, 15323.
V. Volkov, Y. Takaoka, R. Righini Phys.Chem.Chem.Phys., 2009, 11, 9979.

Current studies, under my conduct, concern structural analysis of molecular guests in the phospholipid membrane environments: their structural realizations (along tuatomerization degree of freedom), localization in the membrane, dynamics and possible influence on the hosting matrix.

V. Volkov, R. Righini J. Phys. Chem. B 2009, 113, 16246.
V. Volkov, R. Chelli, F. Muniz-Miranda, R. Righini J. Phys. Chem. B, 2011, 115, 5294.

Recent progress in surface specific infrared spectroscopy, suggests new possibilities to probe and characterized vibrational states at interfaces under conditions close to those in vivo. In particular, sum-frequency generation experiment (χ^-2) provides a unique sensitivity to probe both intra- and inter-molecular correlations in mono- and bi-layers with molecular presence close to that, which is typical accounted in analytical chemistry. There are several subjects I consider for interested students and fellows to unfold during our time together:

1. Phospholipid membrane destabilization with amphiphilic molecular forms: viral protein segments, fertilization polypeptides, and surface active antibiotic. A pilot project: structural properties, dynamics and hydration of gp41 HIV fusion segment in phospholipid membrane
   [Biochimica Biophysica Acta 2002, 1559, 96; Biochemistry 2010, 49, 10623].
2. Control and detection of immunological reactivity mediated by surface. A pilot project: cardiolupin antibody association with a cardiolupin containing phospholipid membrane [Arthritis Research & Therapy 2006, Vol. 8, N 6, page 1]. Specifically, Antiphospholipid antibodies (APLA) are antibodies directed against certain phospholipid-binding proteins such as prothrombin or β2-glycoprotein I. When detected by a clotting assay they are known as "lupus anticoagulants." They can also be measured quantitatively in an ELISA that contains β2-glycoprotein I or cardiolipin. The key point in this experimental direction is to take advantage of both: of the possibility to engineer a Langmuir monolayer precisely in terms of composition and of the possibility to monitor infrared response from a small structural part of interacting molecules selected by the surface. This provides an opportunity to develop an analogy of ELISA test but with a higher analytical specificity.
3. Novel experimental approaches: phase-locked heterodyned χ^-4 experiment, along the line suggested in early work
   [Optics Letters 2005, Vol. 30, Issue 15, 2010].



This project would require some native curiosity in instrumentation and in applied mathematics. Those who have interests in such would be welcome to take part as well.

Regardless, of the topic of interests, a research endeavor with me would require some learning of math and physics. However, together, I believe, we will not have a problem unsolved.


Long-term Partners:

	Prof. Anna Maria Papini Dipartimento di Chimica Organica "Ugo Schiff", Università di Firenze http://www.unifi.it/peptlab/PeptLab/contatti_en.html
	Prof. Wei Zhuang Micromolecule System Dynamics and Ultrafast Spectroscopy Theory Research Group, Dalian Institute of Chemical Physics. http://ultrafast.dicp.ac.cn/EN/
	Dr. Riccardo Chelli Dipartimento di Chimica, Università di Firenze. http://www.chim.unifi.it/~chelli/