Project description:The Fenna-Matthews-Olson protein from Prosthecochloris aestuarii (PaFMO) has been crystallized in a new form that is amenable to high-resolution X-ray and neutron analysis. The crystals belonged to space group H3, with unit-cell parameters a = b = 83.64, c = 294.78?Å, and diffracted X-rays to ?1.7?Å resolution at room temperature. Large PaFMO crystals grown to volumes of 0.3-0.5?mm3 diffracted neutrons to 2.2?Å resolution on the MaNDi neutron diffractometer at the Spallation Neutron Source. The resolution of the neutron data will allow direct determination of the positions of H atoms in the structure, which are believed to be fundamentally important in tuning the individual excitation energies of bacteriochlorophylls in this archetypal photosynthetic antenna complex. This is one of the largest unit-cell systems yet studied using neutron diffraction, and will allow the first high-resolution neutron analysis of a photosynthetic antenna complex.
Project description:Significant protein rearrangement upon excitation and energy transfer in Fenna-Matthews-Olson protein of Prosthecochloris aestuarii results in a modified energy landscape, which induces more changes in pigment site energies than predicted by the "standard" hole-burning theory. The energy changes are elucidated by simulations while investigating the effects of site-dependent disorder, both static (site-energy distribution widths) and dynamic (spectral density shapes). The resulting optimized site energies and their fluctuations are consistent with relative differences observed in inhomogeneous widths calculated by recent molecular dynamic simulations. Two sets of different spectral densities reveal how their shapes affect the population dynamics and distribution of exciton lifetimes. Calculations revealed the wavelength-dependent distributions of exciton lifetimes (T 1) in the femtosecond to picosecond time frame. We suggest that the calculated multimodal and asymmetric wavelength-dependent T 1 distributions offer more insight into the interpretation of resonant hole-burned (HB) spectra, kinetic traces in two-dimensional (2D) electronic spectroscopy experiments, and widely used global analyses in fitting data from transient absorption experiments.
Project description:Black corals, ecologically important cnidarians found from shallow to deep ocean depths, form a strong yet flexible skeleton of sclerotized chitin and other biomolecules including proteins. The structure and mechanical properties of the chitin component of the skeleton have been well-characterized. However, the protein component has remained a mystery. Here we used liquid chromatography-tandem mass spectrometry to sequence proteins extracted from two species of common Red Sea black corals following either one or two cleaning steps. We detected hundreds of proteins between the two corals, nearly 70 of which are each others’ reciprocal best BLAST hit. Unlike stony corals, only a few of the detected proteins were moderately acidic (biased toward aspartic and/or glutamic acid residues) suggesting less of a role for these types of proteins in black coral skeleton formation as compared to stony corals. No distinct chitin binding domains were found in the proteins, but proteins annotated as having a role in protein and chitin modifications were detected. Our results support the integral role of proteins in black coral skeleton formation, structure, and function.