The identification of a novel inositol lipid, phosphatidylinositol trisphosphate (PIP3), in rat cerebrum using in vivo techniques

Rats received intraventricular injections of 20 uCi of [3H]-myo-inositol, and were sacrificed 24 hrs later by high-power head-focused microwave fixation. Two inositol lipid extraction methods were compared: The Hauser and Eichberg method yielded higher recovery of inositol lipids, but a lower inositol phosphate content. The Schacht method yielded reduced radiolabel in the lipid fractions, but increased water soluble phosphates. Both methods extracted a novel inositol lipid (PIP3) which contained inositol tetrakisphosphate (IP4) as its polar head group. This was determined by alkaline hydrolysis and analyzed by high performance liquid chromatography with authentic IP4 standard. Furthermore, preliminary studies of the fatty acid composition indicated a similarity with other inositol lipids. The radiolabel ratio of PIP2:PIP3 was 5:1. In summary, we have isolated a novel inositol phospholipid in rat brain, PIP3, the parent compound for inositol tetrakisphosphate (IP4).

Crystal structure of L-2-oxothiazolidine-4-carboxylic acid

Crystals of the title compound, L-2-oxothiazolidine-4-carboxylic acid, OTC (C4H5NO3S), grown from an aqueous solution are orthorhombic, space group P2(1)2(1)2(1) with the following cell parameters at 22 +/- 3 degrees: a = 5.381(1), b = 5.961(1), c = 17.929(3)A, V = 575.1A(3), Mr = 146.2, Dc = 1.688 g.cm-3, mu = 43.9 cm-1 and Z = 4. The crystal structure was solved by the application of direct methods and refined to an R value of 0.032 for 596 reflections with I greater than 3 sigma(I). The thiazolidine ring adopts a "twist" conformation. This structure contains a short (2.619(3)A) intermolecular hydrogen bond between the carboxyl OH and the oxygen of the 2-oxo moiety, a feature common to most acyl amino acids and acyl peptides.

A model for hydropathy-based peptide interactions

Two peptides are specified when the noncoding DNA strand is read in the 5' to 3', or the 3' to 5' direction, and both peptides form strong complexes with the natural peptide, as found by J. E. Blalock and K. L. Bost with ACTH [1986) Biochem. J. 234, 679-683). We report here that strong hydropathic complementarity (pairing of hydrophobic with hydrophilic residues), the assumed basis of these interactions, is obtained only if the peptide resulting from reading in the 3' to 5' direction is aligned parallel to the natural peptide, or if the peptide derived by opposite reading of the DNA is aligned antiparallel to it. Complementary is abolished in other alignments, including all staggered ones. In the appropriate alignments of the constructs the amino acid residues opposite one another are specified by a pair of complementary codons in the DNA; Blalock and Bost have indeed shown that complementary pairs of codons specify amino acids of opposite hydropathy. A model is proposed to explain how hydropathic complementarity can lead to interaction between peptides. We propose that in the interacting peptides hydrophilic residues of both chains are oriented toward the aqueous solvent, while the hydrophobic ones form the interphase between the two chains. Tight packing is made possible by the stipulation that whenever a hydrophilic residue turns toward the aqueous phase, a space is liberated which can accommodate a hydrophobic residue from the opposing chain. This entropy-driven configuration can lead to strong interactions between portions of peptides consisting of hydropathically complementary residues.

Role of water molecules in the crystal structure of Gly-L-Ala-L-Phe: a possible sequence preference for nucleation of alpha-helix?

The synthetic peptide Gly-L-Ala-L-Phe (C14H19N3O4.2H2O; GAF) crystallizes in the monoclinic space group P2I1), with a = 5.879(1), b = 7.966(1), c = 17.754(2) A, beta = 95.14(2) degrees, Dx = 1.321 g cm-3, and Z = 2. The crystal structure was solved by direct methods using the program SHELXS-86 and refined to an R value of 0.031 for 1425 reflections (greater than 3 sigma). The tripeptide exists as a zwitterion in the crystal and assumes a near alpha-helical backbone conformation with the following torsion angles: psi 1 = -147.8 degrees; phi 2, psi 2 = -71.2 degrees, 33.4 degrees; phi 3, psi 3 = -78.3 degrees, -43.3 degrees. In this structure, one water molecule bridges the COO- and NH3+ terminii to complete a turn of an alpha-helix and another water molecule participates in head-to-tail intermolecular hydrogen bonding, so that the end result is a column of molecules that looks like an alpha-helix. Thus, the two water molecules of crystallization play a major role in stabilizing the near alpha-helical conformation of each tripeptide molecule and in elongating the helix throughout the crystal. An analysis of all protein sequences around regions containing a GAF fragment by Chou-Fasman's secondary structure prediction method showed that those regions are likely to assume an alpha-helical conformation with twice the probability they are likely to adopt a beta-sheet conformation. It is conceivable that a GAF fragment may be a good part of the nucleation site for forming alpha-helical fragments in a polypeptide, with the aqueous medium playing a crucial role in maintaining such transient species.

Crystal structure and conformation of glycyl-glycyl-sarcosine

Crystals of the tripeptide, glycyl-glycyl-sarcosine (C7H13N3O4) from aqueous methanol are orthorhombic, space group Pbcn with cell parameters at 294 K of a = 8.279(1), b = 9.229(4), c = 24.447(5)A, V = 1868.0 A3, M.W. = 203.2, and Z = 8. The crystal structure was solved and refined using CAD-4 data (1171 reflections greater than or equal to 3 sigma) to a final R-value of 0.053. The first peptide linkage is trans and planar whereas the second peptide link between Gly and sarcosine is cis and appreciably non-planar (w = 7.4 degrees). The peptide backbone has an extended conformation at the N-terminal part but adopts a polyglycine-II type of conformation at the C-terminal part. The backbone torsion angles are: psi 1 = -173.9, w1 = -177.8, (phi 2, psi 2) = (-178.8, -170.8), w2 = 7.4, (phi 3, psi 3) = (-81.6, 165.6 degrees).

Crystal structure and conformation of L-pyroglutamyl-L-alanine

Crystals of the dipeptide, pyroglutamyl-alanine (C8H12N2O4) grown from aqueous methanol are monoclinic, space group P2(1) with the following cell parameters: a = 4.863(2), b = 16.069(1), c = 6.534(2)A and beta = 109.9(2) degrees, V = 480.0A3, Mr = 200.2, Dc = 1.385 g cm-3, and Z = 2. The crystal structure was solved by the application of direct methods and refined to an R value of 0.044 for 699 reflections with I greater than 2 sigma. The amide of the pyroglutamyl side chain is cis, omega 1 = 2.6(7) degrees; the peptide unit is trans and appreciably non-planar (omega 2 = 167.4(5) degrees). The backbone torsional angles are: psi 1 = 166.1(5), phi 2 = -90.3(6), and psi 2 = -22.4(6) degrees. This structure contains a short (2.551(5)A) intermolecular hydrogen bond between the carboxyl OH and the N-acyl oxygen, a feature common to most acyl amino acids and acyl peptides.

Conformation and hydrogen bonding of N-formylmethionyl peptides. II. Crystal and molecular structure of N-formyl-L-methionyl-L-phenylalanine

Crystals of N-formyl-L-methionyl-L-phenylalanine (C15H20N2O4S), grown from aqueous methanol solution are orthorhombic, space group, P2(1)2(1)2(1), with cell parameters at 294K of a = 4.900(2), b = 17.947(4), c = 18.726(4)A, V = 1646.8A3, M.W. = 324.4, Z = 4 and Dm = 1.308 g/cc, and as expected, all nearly identical to that of N-f-D-Met-D-Phe studied by Jeffs, Heald, Chodosh & Eggleston (Int. J. Peptide Protein Res. 24, 442-446, 1984). The crystal structure was solved and refined using CAD-4 data (1095 reflections greater than or equal to 3 sigma) to a final R value of 0.042. Molecules related by the alpha-translation form a parallel beta-sheet rather than anti-parallel sheet as stated in the earlier study of Jeffs et al. The formation of the parallel rather than the anti-parallel beta-sheet structure, the use of the C-H ...O hydrogen bonds to stabilize the beta-sheet and the very short O-H ...O hydrogen bond between the carboxyl OH and the N-acyl oxygen atom emerge as the main structural features of the chemotactic N-formyl methionyl peptides.

Short S...O contacts: structure of 2,5-bis(p-methoxyphenylhydroxymethyl)thiophene

C20H20O4S, Mr = 356.4, monoclinic, P2(1)/c, a = 5.045 (3), b = 29.115 (7), c = 11.924 (2) A, beta = 94.82 (3) degrees, V = 1745.2 A3, Z = 4, Dx = 1.357 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 17.86 cm-1, F(000) = 752, T = 298 K, R = 0.038, wR = 0.044 for 1212 reflections, I greater than 3 sigma(I). In the crystal, the molecule adopts a conformation in which one of the two hydroxymethyl fragments is synplanar to S and the other is anticlinal to S. Although the two fragments are otherwise equivalent, the C-C-O bond angles in the two hydroxymethyl fragments are significantly different from each other [106.7 (3) and 110.7 (3) degrees]. The decrease of 4 degrees in the bond angle is for the C-C-OH fragment that makes a short S...O contact and must indicate a non-bonded attractive interaction between the two atoms.

Structure of adenosine-5'-mononicotinate (AMN) trihydrate: an analog of NAD for testing intramolecular stacking

C16H16N6O5.3H2O, Mr = 426.4, monoclinic, P21, a = 9.535 (2), b = 13.932 (2), c = 7.138 (2) A, beta = 93.13 (2) degrees, V = 946.85 A3, Z = 2, Dx = 1.495 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 9.93 cm-1, F(000) = 428, T = 294 K, R = 0.045 and wR = 0.059 for 1460 observed reflections [I greater than 3 sigma (I)]. The AMN molecules, unlike NAD or other model structures of NAD, are not charged and exhibit intra- as well as intermolecular stacking of pyridine ring over adenine ring. There is extensive hydrogen bonding in the crystal involving the pyridine and adenine rings and the three water molecules. Rather surprisingly, the ester carbonyl O atom is not involved in the hydrogen bonding.

Studies on modified nucleic acid bases: structure of 3-isobutyl-1-methylxanthine

C10H14O2, M = 222.3, monoclinic, P2/c, alpha = 4.882 (3), b = 8.715 (1), c = 25.955 (3) A, beta = 92.28 (1) degree, V = 1103.4 (9) A, Z = 4, Dm = 1.34, Dx = 1.338 g cm 3, Cu K alpha, lamba = 1.5418 A, mu = 7.62 cm 1, F(000) = 472, T = 294 k, R = 0.058 for 984 reflections I greater than 3 sigma (1). The isobutyl chain is oriented almost perpendicular to the xanthine ring (C(2)-N(3)-C(31)-C(32) +/- 99.8 (4)degree]. The isobutyl chain torsion angles are N(3)-C(31)-C(32)-C(33) +/- 62.2 (4) and N(3)-C(31) C(32)-C(34) +/- 174.1 (3) degree. The structure forms self-paired dimers of xanthine bases with a pair of N-H...O and a pair of weaker C-H...N hydrogen bonds across centers of inversion. There is a partial stacking of the xanthine bases.

Conformation and sandwiching of bases by azido groups in the crystal structure of 3'-azido-3'-deoxy-thymidine (AZT), an antiviral agent that inhibits HIV reverse transcriptase

The crystal structure of 3'-azido-3'-deoxy-thymidine (AZT), an antiviral agent that inhibits HIV reverse transcriptase, has been determined from three-dimensional x-ray diffractometer data. The crystal structure contains two independent molecules of AZT forming a hydrogen bonded dimer but exhibiting different conformations. These conformations are different from those theoretically calculated by molecular mechanics methods. The azido groups associate with each other and interrupt the base stacking, forming a sandwich of two stacked bases. The close conformational similarity of AZT to thymidine explains why AZT is a good substrate for thymidine kinase. The selective inhibition of reverse transcriptase by AZT is not due to any conformational restrictions imposed by the azido group but likely due to their stereoelectronic properties.

Crystal structure and conformation of polypeptides: L-leucylglycylglycylglycine

Crystals of L-leucylglycylglycylglycine, LGGG (C12H22N4O5), grown from an ethanol-water solution, are orthorhombic, space groups P2(1)2(1)2(1), with unit cell dimensions (at 22 +/- 3 degrees) a = 9.337(1), b = 10.995(1), c = 15.235(1)A, v = 1563.4 A3, Z = 4 with a density of Dobs = 1.29 g.cm-3 and Dcalc = 1.279 g.cm-3. The crystal structure was solved by the application of direct methods and refined to an R value of 0.029 for 1018 reflections with I greater than or equal to 2 sigma. The molecule exists as a zwitterion in the crystal. The trans peptide backbone takes up a folded conformation at the middle glycylglycyl link accompanied by a significant nonplanarity up to delta omega of 8 degrees at the middle peptide and is relatively more extended at the two ends. The molecules are linked together intermolecularly in an infinite sequence of head to tail 1-4' hydrogen bonds, as is typical of charged peptides. It is interesting to note that while glycylglycylglycine takes up an extended beta-sheet conformation, addition of Leu to the N-terminal results in a bent conformation.

Hepatic toxicity in South Indian patients during treatment of tuberculosis with short-course regimens containing isoniazid, rifampicin and pyrazinamide

Results are presented of the incidence of hepatitis, nearly always with jaundice, among 1686 patients in clinical trials of the treatment of spinal tuberculosis, of tuberculosis meningitis and of pulmonary tuberculosis with short-course regimens containing rifampicin, isoniazid, streptomycin and pyrazinamide. The incidence was high in patients treated with daily regimens of isoniazid and rifampicin: 16-39% in children with tuberculous meningitis, 10% in patients with spinal tuberculosis (non-surgical cases), and 2-8% in those with pulmonary tuberculosis. Hepatitis, in those receiving rifampicin occurred more often in slow than in rapid acetylators of isoniazid, the proportions amongst those whose acetylator phenotype had been determined being 11% of 317 slow acetylators and 1% of 244 rapid acetylators. In children with tuberculous meningitis, the risk of hepatitis with isoniazid 20 mg/kg (39%) was higher than that with 12 mg/kg (16%), and appreciably lower in patients given rifampicin twice-weekly (5%) rather than daily (21%). There was no indication that pyrazinamide contributed to the hepatic toxicity.

Structure and conformation of linear peptides. VIII. Structure of t-Boc-glycyl-L-phenylalanine

The crystal structure of t-Boc-glycyl-L-phenylalanine (C14H22N2O5, molecular weight = 298) has been determined. Crystals are monoclinic, space group P2(1), with a = 7.599(1) A, b = 9.576(2), c = 12.841(2), beta = 97.21(1) degrees, Z = 2, Dm = 1.149, Dc = 1.168 g X cm-3. Trial structure was obtained by direct methods and refined to a final R-index of 0.064 for 1465 reflections with I greater than 1 sigma. The peptide unit is trans planar and is nearly perpendicular to the plane containing the urethane moiety. The plane of the carboxyl group makes a dihedral angle of 16.0 degrees with the peptide unit. The backbone torsion angles are omega 0 = -176.9 degrees, phi 1 = -88.0 degrees, psi 1 = -14.5 degrees, omega 1 = 176.4 degrees, phi 2 = -164.7 degrees and psi 2 = 170.3 degrees. The phenylalanine side chain conformation is represented by the torsion angles chi 1 = 52.0 degrees, chi 2 = 85.8 degrees.

The inositol phospholipids: a stereochemical view of biological activity

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Structure and conformation of linear peptides. V. Structure of L-prolyl-glycyl-glycine

The tripeptide, L-prolyl-glycyl-glycine, crystallizes in the trigonal space group P3(2), with a = b = 8.682(2) A, c = 12.008(2) and Z = 3. The structure was solved by direct methods and refined to an R-value of 0.07 for 727 reflections (I greater than 1.0 sigma). The molecule exists as a zwitterion in the crystal. The peptide units are trans and show significant deviations from planarity (omega 1 = 169.7 degrees, omega 2 = -170.1 degrees). The peptide backbone adopts a left-handed helical conformation similar to that of polyglycine II and polyproline II.

Conformation of O6-alkylguanosines: molecular mechanism of mutagenesis

The O6-alkylation of guanine residues in DNA treated with alkylating agents induce mutations due to mis-pairing resulting from the deprotonation of N1. In addition to the deprotonation of N1, the conformation of the O6-alkyl group with respect to N7 of guanine is very important. Here, we present X-ray crystallographic evidence that shows that the methyl group in O6-methylguanosine has a preference for the distal conformation, blocking the Watson-Crick sites. This distal conformation persists in the solid state for several analogs of O6-alkylguanosine also. This preferred conformation agrees with the result that poly(O6-methyl GMP) does not form any stable complex with poly(U). However, the mispairing of O6-methylguanine with thymine and the resultant G----A transition is known from in vitro studies. The above two opposite results strongly indicate that the conformation of the O6-alkyl group and the base pairing properties of O6-alkylguanine at the monomer and polymer levels must be different from the situation when the modified base is embedded with a small frequency in a duplex. It is interesting to note that the sterical blocking of the Watson-Crick site at the monomer level and the altered base pairing properties when present as occasional bases in a duplex emerge as a common property for several mutagenic bases like O6-alkylguanines, O4-methyluracil and N4-hydroxycytosine.

Structure and conformation on linear peptides. VI. Structure of D,L-alanyl-L,D-norvaline

The dipeptide, (DL)-alanyl-(DL)-norvaline, crystallizes in the monoclinic space group P2(1)/c, with a = 12.559(2)A, b = 5.265(1), c = 16.003(3), beta = 103.53(2) degrees, Z = 4. The structure was solved by direct methods and refined to an R-value of 0.054 for 871 reflections with I greater than 2 sigma. The molecule exists as a zwitterion in the crystal. The peptide unit is trans and shows significant deviations from planarity (delta omega = 12.4 degrees). The peptide backbone adopts an extended conformation. The unit cell contains D-Ala-L-norval and its enantiomer. The molecular conformation and packing features show a striking resemblance to those for D-Ala-L-Met (1), and leads to the speculation that norvaline might act as an analog of methionine.

Intercalation of water molecules between nucleic acid bases in the crystal structures of 6-azathymine hemihydrate and 5-amino-2-thiocytosine dihydrochloride dihydrate

The crystal structure of 6-azathymine hemihydrate (6AzTH) exhibits a novel intercalation of water molecules interposed half-way between the modified bases 6.3 to 6.7 A apart. The crystal contains four molecules of 6-azathymine (6AzT) and two water molecules as the independent repeating unit. These two water molecules together with the four bases form two separate water sandwiches. In the crystal structure these sandwiches form two sets of local clusters. The anhydrous crystalline form of 6AzT, on the other hand, is stabilized by base stacking interactions. Both the water molecules in 6AzTH that are involved in sandwich formation have trigonal coordination around them. A reexamination of the crystal structure of 5-amino-2-thiocytosine (5A2TC) revealed that one of the water molecules in this structure also forms a water sandwich and has trigonal coordination whereas the other water molecule with tetrahedral coordination does not form a sandwich. The environment and the characteristics of the intercalated water molecule in these structures suggest a possible role for such water intercalations in the dynamics of DNA. Crystals of 6AzTH are monoclinic, space group P21/n, with unit cell parameters a = 8.861 (1), b = 13.177 (3), c = 20.662 (2) A, beta = 93.35 (1) degrees, and Z = 16. From diffractometer data (2503 reflections, greater than or equal to 3 sigma), the crystal structure was solved and refined to an R of 0.056.

Conformational variability of NAD+ in the free and bound states: a nicotinamide sandwich in NAD+ crystals

X-ray analysis of the free-acid crystal form of the coenzyme nicotinamide adenine dinucleotide (NAD+) revealed a conformational difference between the free NAD+ molecule and one bound in enzymes or complexed to Li+ ions. The pyrophosphate group showed asymmetry in the phosphate-oxygen bonds of the phosphate-oxygen-phosphate link; this bond at the nicotinamide side of the link is longer than that at the adenosine side by 0.04 angstrom. The crystal structure showed a novel intermolecular stacking of adenine and water molecules on opposite sides of nicotinamide that gives rise to a nicotinamide sandwich.

Conformation and hydrogen bonding of N-formylmethionyl peptides. Parallel beta-sheet in the crystal structure of N-formyl-L-methionyl-L-valine

Crystals of N-formyl-L-methionyl-L-valine (C11H20N2O)4S, M.W. = 276.3) are orthorhombic, space group )2(1)2(1)2(1) with cell constants at 294K of a = 4.851 (1), b = 14.925 (1), c = 19.745 (3) A, V = 1429.8 (1) A3, Z = 4 and observed (Dm) and calculated (Dx) of 1.49 and 1.488 g x cm-3, respectively. The crystal structure was solved using automatic diffractometer data (1260 reflections larger than or equal to 3 sigma) and refined to a final R-value of 0.035. This structure contains a short (2.626 (3) A) intermolecular hydrogen bond between the carboxyl OH and the N-acyl oxygen, a feature common to most N-acylamino acids and N-acylpeptides. The peptide is nearly planar (omega = 174.6 (5)); the values of psi 1, phi 2, psi 1T and psi 2T are, respectively, 131.8 (4) degrees, -139.9 (5) degrees, -39.3 (4) degrees and 142.1 (4) degrees. The methionine side chain is not zig-zag transplanar; the side chain torsion angles are: chi 1(1) = -60.0 (4) degrees, chi 2(1) = 176.0 (4) degrees and chi 3(1) = 71.8 (4) degrees. The two C gamma's for valine have psi 1-values of -64.4 (5) degrees and 173.7 (5) degrees. The formation of the parallel rather than antiparallel beta-sheet structure, the participation of the N-formyl group in the parallel beta-sheet and the use of C-H ... O hydrogen bonds to stabilize the beta-sheet are novel features found in this structure.

Anxiety provoking situations in Indian families

Life situations pertaining to the relationship dimension are viewed in respect of families of anxiety patients and normals. Grand-parents' interference, parents-in-law relationships, parents' role functioning, siblings' interaction, marital relationships and other relatives' cooperation are studied for 20 anxiety patients and 40 normals based on group matching. It was found that frequent interference of grand-parents, dissatisfaction with parents-in-law, inadequate mutually contradictory parents' role functioning, disharmonious siblings interaction, threatening and conflicting marital life and lack of cooperation and support on the part of other relatives seem to be sources of anxiety in the Indian setting.

Lack of relationship between hepatic toxicity and acetylator phenotype in three thousand South Indian patients during treatment with isoniazid for tuberculosis

The results are presented of a retrospective analysis of the incidence of jaundice among 3,000 patients with pulmonary tuberculosis and of the activities of serum aspartate aminotransferase among 850 according to their isoniazid acetylator phenotype. The patients had been treated with a variety of isoniazid-containing regimens in a series of controlled clinical trials in South India. The results show that rapid acetylators are no more prone to develop isoniazid-induced hepatic toxicity than are slow acetylators.

Classes of unitarizable derived functor modules

For a real semisimple Lie group G, the description of the unitary dual remains an elusive question. One of the difficulties has been the lack of technique for constructing unitary representations. Unitary induction from parabolic subgroups of G yields unitary representations by the very definition of these representations. However, not all unitary irreducible representations of G are obtained by this type of induction. In addition, we need derived functor parabolic induction [ef. Vogan, D. (1981) Representations of Real Reductive Lie Groups (Birkhäuser, Boston)] to describe all irreducible representations of G. For this second type of induction, the obvious analogues from parabolic subgroup induction regarding unitarity are false. In this announcement, we describe a setting where derived functor parabolic induction yields unitary representations of G. These results include proofs of unitarity for some of the representations conjectured to be unitary by Vogan and Zuckerman [(1983) Invent. Math., in press] and also proofs of unitarity for some which lie outside the domain described in those conjectures.

Lipids and cholesterol esterifying enzyme changes by Anna Pavala Sindhooram therapy in experimental rat hyperlipaemia

The effect of Anna Pavala Sindhooram (APS), an indigenous drug showing lipid lowering action was tested in experimental rat atherosclerosis induced by feeding an atherogenic diet. APS was found to decrease the levels of serum cholesterol and phospholipids while triglycerides remained unaffected in atherogenic diet fed rats. Lipid levels in the aorta, liver and intestine were also increased by atherogenic diet feeding, and APS administration with diet restriction reversed this trend. Cholesterol ester was lowered. Both cholesteryl ester hydrolase (CEH) and synthetase (CES) activities in the tissues were elevated while the CEH/CES ratio was lowered in atherosclerosis. APS administration led to a decrease in enzyme activities and an increase in the CEH/CES ratio. APS in vitro inhibited both enzyme activities. NMR spectroscopic studies showed that the soluble components of APS bind or modify cholesterol. Iron, copper, magnesium and calcium present in APS may play a role in the removal of cholesterol ester from the aorta and its disposal.

X-ray structure of a dinucleoside monophosphate A2'p5'C that contains a 2'-5' link found in (2'-5')oligo(A)s induced by interferons: single-stranded helical conformation of 2'-5'-linked oligonucleotides

In order to understand why DNA and RNA have the 3'-5' and not the 2'-5' link and to delineate the stereochemistry of the 2'-5' phosphodiester links, we crystallized and carried out a very accurate x-ray diffraction analysis of A2 p5'C, an analog of A2' p5'A. Contrary to numerous reports in the literature that conclude that the tendency for 2'-5' nucleotides to stack intramolecularly is stronger than for 3'-5' counterparts, we find hardly any intramolecular base stacking for this molecule but find an intramolecular "stacking" of the ribose oxygen-4' of cytidine on top of the adenine ring. Although A2' p5'C shows the standard conformational features usually found for 3'-5' nucleotides, the overall stereochemistry of 2'-5' nucleotides is quite different because the 2' link orients the backbone inwards to the bases unlike the 3' and 5' links that orient it away from the bases. With the conformational features found for A2' p5'C, it is possible to build a very compact right-handed single-stranded helix but not a double helix. Such a preference for single-stranded helices may be the reason for the absence of 2'-5' bonds in DNA and RNA even though the 2'-5' bonds are formed more readily then 3'-5' bonds.

Extension of mental health service through psychiatric camps : a new approach

Psychiatric camps in the manner they are usually conducted serve no useful purpose in the long run, except to identify cases and to increase people's awareness about mental illnesses. The main drawback is poor follow up of the cases detected.To overcome these drawbacks and to make these camps more useful in delivering mental health services to the community, a new approach is being worked out. Screening and selection of the patients for the camp by the local doctors with the help of symptom check-list, a good propaganda well in advance incorporating the cardinal symptoms through mass media, training of the local doctors to gain basic skills and knowledge to manage cases during follow up, periodic visits by the psychiatrists to help these doctors in this job for some time, mental health exhibition during the camp were some of the strategies adopted in Kollegal Neuropsychiatric camp by community psychiatry unit of NIMHANS.It was a three days' camp. 312 cases were registered after screening. Only 6.7% cases were non-psychiatric. 30% epileptics, 30% neurotics, 12% Headache, 9% MR, 9% neurological cases, 5% psychoses. 25 doctors participated in training programme and camp patients were allotted to them for follow up. Monthly follow up is in progress. Findings and experiences are discussed.

New patterns of hydrogen bonded interactions between polypeptide chains. Crystal and molecular structure of glycylglycylglycine

Crystals of glycylglycylglycine (C6H-11N3O4), grown from an aqueous methanol solution, are triclinic, space group P1, with the unit cell dimensions (at 22 +/- 3 degrees) a = 11.656(3), b = 14.817(3), c = 4.823(2) A, alpha = 88.45(3), beta = 95.96(3), gamma = 105.42(3) degrees, Z = 4 (with two molecules in the asymmetric unit) with a density of Dobs = 1.58 g X cm -3 and Dcalc = 1.572 g X cm -3. The crystal structure was solved by a combination of multisolution and trial and error methods and refined with full-matrix least-squares method to a final R value of 0.036 for the observed 3021 reflections (I greater than or equal to 2 sigma). The conformation of the two molecules I and II in the asymmetric unit is very similar (except around the N-terminal end); they have the fully extended trans-planar conformation, and have omega values ranging from 2 to 4 degrees. The peptide chain repeating distances (C1 alpha - C3 alpha) are 7.27 A and 7.18 A in the two molecules as compared with the value of 6.68 A for extended beta-sheets with beta-carbons. There are four different interactions between these two molecules characterized by different hydrogen bonding. Molecule I is hydrogen bonded to a neighboring molecule I using four hydrogen bonds. Molecule II is hydrogen bonded to another II, using bifurcated interactions involving the peptide nitrogen. Molecule I is hydrogen bonded to two different molecules II forming distinctly different hydrogen bonding patterns from the two mentioned above. The molecules are packed in rows, in a head-to-tail fashion (C-terminal opposite N-terminal) and are held together in sheets by hydrogen bonds between carbonyl and amide groups, corresponding to the very familiar anti-parallel pleated sheet arrangement for polypeptides. The hydrogen bonds involving the amino nitrogens as donors are significantly longer and presumably weaker compared to those involving the NH+3 group. The C=O distances show variations that correlated with hydrogen bonding. The N-H...O angle varies from 152 to 174 degrees and the bent N-H...O hydrogen bonds show bifurcated interactions.