C. S. Yoo

Effect of Baclofen Enantiomorphs on the Spinal Trigeminal Nucleus and Steric Similarities of Carbamazepine

The seemingly structurally different drugs, baclofen and carbamazepine, have a similar neurophysiologic effect on the cat spinal trigeminal nucleus and a similar clinical effect in the amelioration of trigeminal neuralgia pain. In this investigation, we report on the enhancement of segmental inhibition by carbamazepine and l-baclofen; d-baclofen produced no effect on segmental inhibition. Doses of l-baclofen one fifth its equivalent racemic dosage produced a much greater enhancement of segmental inhibition. d-Baclofen, when given prior to l-baclofen, blocked the effect of l-baclofen on segmental inhibition and the unconditioned response at previously effective doses. Pretreatment with d-baclofen also blocked the effect of subsequent carbamazepine on segmental inhibition, but had no effect on the unconditioned response. Crystallographic evaluation of carbamazepine and the enantiomorphs of baclofen revealed a surprisingly good fit of baclofen isomers to moieties of the carbamazepine molecule. The results suggest that the baclofen enantiomorphs and carbamazepine have a common mechanism of action in the cat spinal trigeminal nucleus, and that d-baclofen, though inactive, is capable of interfering with the effect of l-baclofen and to a lesser extent with carbamazepine.

Crystal structure of Bence Jones protein rhe (3 A) and its unique domain-domain association.

Abstract The crystal structure of protein Rhe, a lambda type VL dimer, has been determined at a resolution of 3 A by the method of multiple isomorphous replacement supplemented with anomalous scattering data. A crystallographic sequence was assigned from an interpretation of the electron density map in an optical comparator and is compared with a chemically determined partial amino acid sequence. The monomeric unit of Rhe, as determined crystallographically, contains 113 amino acids, 110 belonging to the variable region and three belonging to the constant segment of a light chain. The single polypeptide chain constituting the monomer forms a nine-stranded β-barrel characteristic of V domains. The β-pleated sheet surrounds an ellipsoidally shaped interior core of approximately 10 A × 15 A × 25 A in size. The monomers that are related by the crystallographic dyad are held together as dimers by interdomain hydrogen bonds and hydrophobic interactions. At one end of the dimer is an opening which is lined exclusively by residues from the hypervariable regions. A comparison of Rhe with Rei, a kappa type VL dimer (Epp et al., 1975), revealed that monomers of Rhe and Rei dimerized differently. Their respective dyad and pseudodyad of dimerization are not the same, and this causes a variation in the overall steric arrangement of the hypervariable regions in the two cavities. In adition a dissimilarity was observed in the non-hypervariable segment linking the first and second hypervariable regions. This segment is in the form of a loop and it includes most of the residues participating in the interdomain interactions stabilizing dimer formation in both proteins and these loop positions differ by as much as 7 A. Our results also show that there is a good correlation between the dissimilarity of the loop position and the difference in the domain-association. Our preliminary analysis indicates that the positions of the corresponding non-hypervariable loops in V domains may be determined in part by the residues in the hypervariable regions. Accordingly, the three-dimensional structure of Rhe suggests that this nonhypervariable loop in VL and its counterpart in VH may have an important biological function in antibody specificity and variability by virtue of their influence over the architecture of the complementarity site.

Structure and Absolute Configuration of (R)-Baclofen Monohydrochloride

C~oHI3C1NO+.C1 -, M, = 250.13, ortho- rhombic, P2~2t2 ~, a = 6.373 (1), b = 7.318 (2), c = 25.699 (5) A, 2(Cu) = 1.54180 A, V= 1198.5 A 3, Z = 4, D c- 1.386 g cm -3, ~ = 47.35 cm-k The phase problem was solved by the direct method (MULTAN 78); R(F) -- 0.029 for 1169 reflections. The molecules are linked into infinite chains along the b axis by hydrogen bonding. There is no significant ring stacking. Introduction. Baclofen (y-amino-fl-(p-chlorophenyl)- butyric acid) is a derivative of the inhibitory neuro- transmitter y-aminobutyric acid (GABA) but, unlike GABA, it can cross the blood/brain barrier (Birkmayer, 1972). It has been shown that baclofen reduces excitatory transmitter effects, especially sub- stance P (Pier & Zimmerman, 1973; Polc & Haefely, 1976; Potashner, 1979; Saito, Konishi & Otsuka, 1975). Baclofen has become the drug of choice in the treatment of spasticity of spinal origin due to its antispastic efficacy at doses which do not produce Cl sedation, its low frequency of serious side effects and its 0(1) lack of organ toxicity (Sachais & Logue, 1977). Recent o(2) studies have shown baclofen to be a promising new N drug in the treatment of the paroxysmal pain of c(1) trigeminal neuralgia (Fromm, Terrence, Chattha & c(2) Glass, 1980). c(4) White, tabular crystals were grown from water by c(5) slow evaporation. The space group was uniquely C(6) determined from Weissenberg photographs as P212~21. C(7) The unit-cell parameters were obtained from a least- c(8) squares fitting of the setting angles for 12 reflections c(10) measured on a Picker FACS-1 diffractometer. The H(O) intensity data were collected using graphite-mono- H 1(2) chromated Cu Ka radiation with the 0:20 scan H2(2) technique. Within the 20 range of 5.0 ° to 125.0 °, 68 Hl(4) out of 1 169 reflections were considered unobserved by H2(4) the criterion I < 3o(1). The E map generated by H(6) MULTAN 78 (Main, 1978) revealed positions of two H(7) CI atoms. All C and N atoms were located from a H(10) subsequent Fourier synthesis. The structure was refined by the full-matrix least-squares refinement procedures and all H atoms (with the exception of those of the NH 3 group) were located in a difference Fourier map. A close look at the difference Fourier map around N showed vague positions of three H atoms. The coordinates of these H atoms were fixed from consideration of the hydrogen bonding to CI-. In the final stages of the refinement all atoms except H were refined with anisotropic temperature factors. The final R factor is 0.029 while the weighted R factor,

Crystals of a bovine neurophysin II-dipeptide amide complex☆

Bovine neurophysin II, a hormone carrier protein, has been crystallized as a binary complex with l-phenylalanyl-l-tyrosine amide, a peptide known to bind neurophysin at its hormone binding site. The crystals belong to space group P212121 with cell constants of a = 121.6(10) A, b = 67·9(6) A and c = 62·1(6) A. The density of the crystal is 1.156 g/cm3. There is a tetramer or two dimers in an asymmetric unit.

Structure of Bence--Jones protein, Pav: an initial report.

Abstract A Bence-Jones protein, Pav, was isolated from the urine of a myeloma patient. Crystals were grown by five different methods yielding different morphologies with slightly changed cell parameters, but the space group was the same (P212121) in every case and X-ray patterns appeared to be identical. The cell parameters are: a = 93.6 (4) to 95.1(4) A , b = 92.7(3) A and c = 72.8(2) A . The crystal density and solvent content are approximately 1.128 g/cm3 and 0.64, respectively. Chemical evidence suggest that the two subunits of Pav are identical in chemical sequence. The crystal structure may prove useful in defining allosteric effects among antibody domains.

Crystals of pig heart aconitase

Aconitase and an isozyme have been crystallized. The space group is P21212 with cell parameters of a = 174·1(9), b = 72·0(4) and c = 72·8(4) . However, the crystals grow either in clusters of multiplets or as twins which are related to each other by a rotation of 90° around the a-axis. The molecular weight based on density measurements is 65,000 ± 3250 with four molecules in the unit cell.

Angle settings for rotation around the diffraction vector for four‐circle diffractometers

Simple graphical representations have been found which have led to the discovery of new geometrical relations between the angle settings, χ0, ω, χ and ϕ-ϕ0, of a four-circle single-crystal diffractometer, and the azimuthal angle, ψ, of the diffraction vector. The new geometric relations greatly simplify the derivation of the trigonometric equations which relate the angle settings with the rotation around the diffraction vector. One of these equations, tan χ = tan χ0/cos (ϕ - ϕ0), is given here for the first time. The others are similar in form to those derived previously with matrix methods.