The energetic fitness of histidine in each of its three protonation states has been investigated for NMRdetermined protein structures by using molecular mechanics calculations. The protein structures have been taken from the Protein Data Bank (PDB). For the proteins in the database, we generated all isomers, considering all combinations of protonation forms of each histidine. The energy of each...

Peptide binding to class II MHC proteins occurs in acidic endosomal compartments following dissociation of class II-associated invariant chain peptide (CLIP). Based on peptide binding both to empty class II MHC and to molecules preloaded with peptides including CLIP, we find evidence for two isomeric forms of empty MHC. One (inactive) does not bind peptide. The other (active) binds peptide rapi...

The pharmacokinetics of dand /-Citrovorum factor (CF) are quite different with respect to the postdistributional plasma decay rates. The natural (/) isomer had a half-life (/?) of 47 ±4 (S.E.) min compared to 143 ± 15 min for the unnatural (d) isomer. Renal clearance was the same for both isomers and was proportional to glomerular filtration rate. Urinary excretion appeared to be the only rou...

The pharmacokinetics of d- and l-citrovorum factor (CF) are quite different with respect to the postdistributional plasma decay rates. The natural (l) isomer had a half-life (beta) of 47 +/- 4 (S.E.) min compared to 143 +/- 15 min for the unnatural (d) isomer. Renal clearance was the same for both isomers and was proportional to glomerular filtration rate. Urinary excretion appeared to be the o...

The molecular rotor 9-(2-Carboxy-2-cyanovinyl)julolidine (CCVJ) exists in two isomers. While the E isomer, which is present absence of light, yields a fluorescent behavior, Z isomer photoproduct with no detectable luminescence. This regenerative behavior utilized for Molecular Tagging Velocimetry (MTV).

Chiral recognition of protein-binding sites by a simple organic molecule with selectivities >100 is reported here. The l-isomer of 4(1-pyrene)-3-butyroyl-phenylalanine amide (Py-L-Phe) binds to BSA with an affinity constant (K(b)) of 3 x 10(7) M(-1), whereas the corresponding D-isomer (Py-D-Phe) binds 100 times weaker. The enantiomers showed contrasting spectral changes when bound to BSA. Where...