04/27/17 -9:45 AM to 11:00 AM
Crawford Memorial Lecture: Professor Stephen Meech
Bryce L. Crawford Memorial Lecture
"Photo-switches in Chemistry and Nature – Time Resolved Studies"
Nature has evolved numerous light driven switches with diverse mechanisms and applications. The most obvious example is in our eyes (rhodopsin), but photoswitches have now been found in many organisms that benefit from the detection of light. In the past 30 years, chemists have begun to compete with nature, developing molecular photoswitches and motors that are designed to power a variety of nanomolecular machines. Lying somewhere between these two is the recently developed method of optogenetics, where the tools of chemical biology are used to impart photoactivity to a biological process, giving the researcher spatial and temporal control over specific cellular responses.
What these diverse switches have in common is their ability to convert the energy in a photon into mechanical motion. This could involve a simple cis-trans isomerization (e.g. in azobenzenes) which can have a synthetically imposed directionality (as in molecular motors). Photo-sensing proteins are more complex, with different chemical reactions (proton transfer, covalent bond formation, isomerization) giving rise to subtle changes in protein structure, which are coupled to subsequent signalling events. Our laboratory, in collaboration with others, is attempting to track the mechanism of light driven structure changes in photoswitches using the tools of time resolved spectroscopy, especially femtosecond to microsecond vibrational spectroscopy. I will present two examples, one from chemistry (the unidirectional molecular motor) and one from biology (the photoactive fluorescent protein dronpa). The interplay of time resolved optical spectroscopy (time resolved fluorescence, Raman, IR . . .) with synthetic chemistry and biological chemistry will be highlighted, and finally I will show (confess?) that the interpretation of our data ultimately requires input from theory and computational chemistry.
Professor Stephen Meech earned his bachelor’s degree in chemistry from the University of East Anglia, and his doctorate from the University of Southhampton/Royal Institution. He was a post-doctoral research associate at Wayne State University in Detroit, and the Royal Institution in London. Prior to joining the University of East Anglia (UEA), he was an Inoue Foundation fellow at the Institute for Molecular Science in Japan, and an Engineering and Physical Sciences Research Council fellow at the University of Groningen, The Netherlands. Professor Meech has been at University of East Anglia since 1994. He has held two Japan Society for the Promotion of Science fellowships in Japan and was a visiting researcher at RIKEN, Tokyo.
Professor Meech's research is focused on understanding ultrafast dynamics of complex condensed phase systems and interfaces, including ultrafast spectroscopy, photoactive proteins, and excited state dynamics. His principal research interest is in the development and application of ultrafast methods in spectroscopy. Current methods include ultrafast two-dimensional spectroscopy (with Ismael Heisler, UEA) ultrafast (sub 50 fs) fluorescence up-conversion, transient absorption and optical Kerr effect spectroscopy. These are applied to investigate a number of complex systems including: coupled chromophore arrays; molecular motors; photoactive fluorescent proteins; blue light sensing proteins; and molecular structure and dynamics in aqueous solution. He maintains a number of national and international research collaborations, which facilitate the application of ultrafast methods to some of the most interesting and challenging problems.
Bryce L. Crawford
Bryce L. Crawford Jr. was a renowned Department of Chemistry professor and scientist. He died in September 2011, at the age of 96. He joined the department in 1940, and became a full professor of physical chemistry in 1946. He was chair of the department from 1955 to 1960, and was dean of the graduate school from 1960 to 1972. He retired in 1985. He loved studying molecular vibrations and force constants, and the experimental side of molecular spectroscopy and molecular structure. During World War II, Crawford worked in research on rocket propellants, making significant contributions to rocketry, and the development of solid propellants for the much larger rockets that evolved after the war. Crawford received many honors during his career, including the prestigious American Chemical Society Priestley Medal; and being named a Fellow of the Society for Applied Spectroscopy, a Guggenheim Fellow at the California Institute of Technology, and a Fulbright Fellow at Oxford University. He held the distinction of membership in three honorary science academies, and was actively involved in many professional associations.