Christopher Gisriel

Photosynthesis is perhaps the most important biological mechanism to have ever evolved. It converts the energy from sunlight into chemical potential energy, and therefore serves as the gateway for nearly all the energy in our biosphere. When photosynthesis is driven by reducing equivalents derived from water (i.e., water-splitting), it is termed “oxygenic photosynthesis”. Oxygenic photosynthesis has defined Earth’s atmospheric and geological composition. It provides the molecular oxygen required for all higher life on Earth.

A vital aspect of photosynthesis is the conversion of light energy into chemical energy. Central to this process are macromolecules called photosystems. These are multi-subunit, cofactor-rich, transmembrane pigment-protein complexes – ideal bioenergetic systems for investigation. Upon light absorption, they transfer energy among cofactors, eventually resulting in charge separation, generating the low potential reducing equivalents used to drive downstream metabolism.

The Gisriel Lab (pronounced like “Israel” but starts with a hard “G”) investigates the molecular mechanisms, diversity, and evolution of the photosystems involved in oxygenic photosynthesis by using structural biology techniques. This reveals fundamental aspects of biology on the molecular scale and features of natural systems that could be used to engineer certain traits into other photosynthetic organisms.

To determine molecular structures of the photosystems, the Gisriel Lab primarily employs cryogenic electron microscopy (cryo-EM). This powerful technique has transformed many fields of research, but in photosynthesis research has allowed the visualization of some photosystem complexes to resolutions better than even 2.0-Å (i.e., incredible detail is revealed). Due to the unique complexity of the photosystems, the Gisriel Lab also develops methods for cryo-EM that help assign cofactors and characterize damage during cryo-EM experiments.