Spin-torch experiment on reaction centers of Rhodobacter sphaeroides

Photosynthesis is the physico-chemical process by which plants, algae and photosynthetic bacteria use light energy to drive the synthesis of organic compounds. Light-induced electron transfer in photosynthetic reaction centers (RCs) is highly efficient, having a quantum yield close to unity. In RCs of Rhodobacter (R.) sphaeroides wild type (WT), the primary electron donor is a bacteriochlorophyll a (BChl) dimer, called the Special Pair P, comprising two dimer halves PL and PM. Two additional BChl cofactors called accessory BChls (BA and BB), two bacteriopheophytins (_A and _B), two quinones and a non-heme iron are organized into two pseudo-symmetric branches named A and B. After the photo excitation the electron is transferred only via the active __A__ branch. On the other hand, in structurally similar RCs, as that of photosystem I, the electron transfer occurs equally over both branches. Neither the reason for the high efficiency nor that of the directionality of the electron transfer has been elucidated so far. To solve these questions, the solid-state photo-chemically induced nuclear polarization (photo-CIDNP) effect with its dramatic enhancement of local NMR signals provides an analytical tool especially suited for studying electron transfer in photosynthetic RCs. In fact, photo-CIDNP MAS NMR has been applied to explore electronic structures of the electron donors and acceptors in RCsUBL - phd migration 201

The resting oxidized state of small laccase analyzed with paramagnetic NMR spectroscopy

nuclei. Two sequence-specific assignments are proposed on the basis of a second-coordination shell variant that also lacks the copper ion at the T1 site, SLAC-T1D/Q291E. This double mutant is found to be exclusively in the RO state, revealing a subtle balance between the RO and the NI states.NWONWO-BOO 022.005.029Macromolecular BiochemistrySolid state NMR/Biophysical Organic Chemistr

Symmetry break of special pair: photochemically induced dynamic nuclear polarization NMR confirms control by nonaromatic substituents

Solid state NMR/Biophysical Organic Chemistr

Large-scale in vitro production, refolding and dimerization of PsbS in different microenvironments

Solid state NMR/Biophysical Organic Chemistr

Bacteriopheophytin a in the active branch of the reaction center of Rhodobacter sphaeroides is not disturbed by the protein matrix as shown by C-13 photo-CIDNP MAS NMR

Solid state NMR/Biophysical Organic Chemistr

wPMLG-5 Spectroscopy of self-aggregated BChl e in natural chlorosomes of Chlorobaculum limnaeum

Solid state NMR/Biophysical Organic Chemistr

Rigidified and Hydrophilic DOTA-like Lanthanoid Ligands: Design, Synthesis, and Dynamic Properties

Limiting the dynamics of paramagnetic tags is crucial for the accuracy of the structural information derived from paramagnetic nuclear magnetic resonance (NMR) experiments. A hydrophilic rigid 2,2 ',2 '', 2"'-( 1, 4,7, 10-tetraaz acyclo do de cane-1,4,7,10-tetrayl)tetraacetic acid (DOTA)-like lanthanoid complex was designed and synthesized following a strategy that allows the incorporation of two sets of two adjacent substituents. This resulted in a C2 symmetric hydrophilic and rigid macrocyclic ring, featuring four chiral hydroxyl-methylene substituents. NMR spectroscopy was used to investigate the conformational dynamics of the novel macrocycle upon complexation with europium and compared to DOTA and its derivatives. The twisted square antiprismatic and square antiprismatic conformers coexist, but the former is favored, which is different from DOTA. Two-dimensional 1H exchange spectroscopy shows that ring flipping of the cyclen-ring is suppressed due to the presence of the four chiral equatorial hydroxyl-methylene substituents at proximate positions. The reorientation of the pendant arms causes conformational exchange between two conformers. The reorientation of the coordination arms is slower when the ring flipping is suppressed. This indicates that these complexes are suitable scaffolds to develop rigid probes for paramagnetic NMR of proteins. Due to their hydrophilic nature, it is anticipated that they are less likely to cause protein precipitation than their more hydrophobic counterparts.Bio-organic SynthesisMacromolecular Biochemistr

Spectral editing through laser-flash excitation in two-dimensional photo-CIDNP MAS NMR experiments

Solid state NMR/Biophysical Organic Chemistr

The field-dependence of the solid-state photo-CIDNP effect in two states of heliobacterial reaction centers

Solid state NMR/Biophysical Organic Chemistr

Chemical exchange at the tri-nuclear copper centre of small laccase from Streptomyces coelicolor

The trinuclear copper center (TNC) of laccase reduces oxygen to water with very little overpotential. The arrangement of the coppers and ligands in the TNC is known to be from many crystal structures, yet information about possible dynamics of the ligands is absent. Here, we report dynamics at the TNC of small laccase from Streptomyces coelicolor using paramagnetic NMR and electron paramagnetic resonance spectroscopy. Fermi contact-shifted resonances tentatively assigned to histidine Hd1 display a two-state chemical exchange with exchange rates in the order of 100 s1 . In the electron paramagnetic resonance spectra, at least two forms are observed with different gz-values. It is proposed that the exchange processes reflect the rotational motion of histidine imidazole rings that coordinate the coppers in the TNC.Macromolecular BiochemistrySolid state NMR/Biophysical Organic Chemistr