01313nas a2200217 4500008004100000022001400041245009500055210006900150260011000219300001400329490000700343520043700350100003300787700002200820700002500842700002400867700002100891700003500912700002800947856012000975 2015 eng d a1477-052000aReversal of H-bonding direction by N-sulfonation in a synthetic reverse-turn peptide motif0 aReversal of Hbonding direction by Nsulfonation in a synthetic re aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAR a3064-30690 v133 a

This communication depicts an intriguing example of hydrogen-bonding reversal upon introduction of a sulfonamide linkage at the N-terminus of a synthetic reverse-turn peptide motif. The ready availability of two sulfonyl oxygen atoms, as hydrogen-bonding acceptors, combined with the inherent twisted conformation of sulfonamides are seen to act as switches that engage/disengage the hydrogen-bond at the sticky ends/termini.

1 aVijayadas, Kuruppanthara, N.1 aKotmale, Amol, S.1 aThorat, Shridhar, H.1 aGonnade, Rajesh, G.1 aNair, Roshna, V.1 aRajamohanan, Pattuparambil, R.1 aSanjayan, Gangadhar, J. uhttp://library.ncl.res.in/content/reversal-h-bonding-direction-n-sulfonation-synthetic-reverse-turn-peptide-motif-001977nas a2200193 4500008004100000022001400041245007100055210006900126260011000195300001400305490000700319520123400326100002001560700002101580700002201601700003501623700002801658856009701686 2015 eng d a1144-054600aRole of N-terminal proline in stabilizing the Ant-Pro zipper motif0 aRole of Nterminal proline in stabilizing the AntPro zipper motif aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAR a3327-33320 v393 a

Hetero-chiral hybrid peptides of the general sequence (L)alpha beta(D)(n)alpha beta(n) featuring proline (Pro, a constrained alpha-amino acid) and anthranilic acid (Ant, a constrained beta-amino acid) as building blocks, where n = 2, 4 etc., form a three-dimensional zipper-like architecture. These zipper peptides attain stable conformation by balancing the co-operative contribution of two competing non-covalent forces, namely hydrogen bonding and aromatic stacking. However, the selection of the N-terminal residue also stands to be one of the key contributors in stabilising the unusually long-range intramolecular hydrogen bond, featuring 26 atoms in the H-bonded ring observed at the termini. This article deals with the substitution alterations at the N-terminus of the zipper motif and their consequent influences on its structure and stability. In this study, the N-terminal Pro residue of the zipper motif was substituted with a flexible amino acid, alanine, and a constrained acyclic amino acid, 2-aminoisobutyric acid, to investigate the role of N-terminal proline in stabilizing the Ant-Pro zipper motif, and its stabilities were assessed by employing solution-state NMR and restrained MD simulation studies.

1 aKheria, Sanjeev1 aNair, Roshna, V.1 aKotmale, Amol, S.1 aRajamohanan, Pattuparambil, R.1 aSanjayan, Gangadhar, J. uhttp://library.ncl.res.in/content/role-n-terminal-proline-stabilizing-ant-pro-zipper-motif-001435nas a2200229 4500008004100000022001400041245010700055210006900162260011000231300001600341490000600357520050500363100002200868700003300890700002200923700001900945700002300964700002400987700003501011700002801046856013101074 2016 eng d a2046-206900aResidue dependent hydrogen-bonding preferences in orthanilic acid-based short peptide beta-turn motifs0 aResidue dependent hydrogenbonding preferences in orthanilic acid aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAR a35328-353310 v63 a

This communication describes the competition between native beta-turn (C10) and 2-aminobenzenesulfonic acid (SAnt)( orthanilic acid)-based pseudo beta-turn (C11) in their hybrid peptides. Solid-state crystal structure and solution-state NMR studies revealed that C10 and C11 can be simultaneously observed under appropriate conditions. The variable temperature NMR coefficient data suggest that the isolated C11/C14 hydrogen bond is weaker in comparison with the consecutive C10 and C11 turns.

1 aJedhe, Ganesh, S.1 aVijayadas, Kuruppanthara, N.1 aKotmale, Amol, S.1 aSangtani, Ekta1 aShinde, Dinesh, R.1 aGonnade, Rajesh, G.1 aRajamohanan, Pattuparambil, R.1 aSanjayan, Gangadhar, J. uhttp://library.ncl.res.in/content/residue-dependent-hydrogen-bonding-preferences-orthanilic-acid-based-short-peptide-beta-turn02657nas a2200205 4500008004100000245010100041210006900142260000800211300001400219490000700233520190800240100002502148700002402173700002202197700002002219700002402239700003502263700002402298856012902322 2017 eng d00aReactivity of difunctional polar monomers and ethylene copolymerization: a comprehensive account0 aReactivity of difunctional polar monomers and ethylene copolymer cAUG a5748-57580 v503 aA comprehensive picture of insertion of 1,1-disubstituted difunctional olefins, their ability to double the functional group density at the same level of incorporation as that of monofunctional olefin, and copolymerization with ethylene has been demonstrated. Exposure of a palladium complex [{P boolean AND O}PdMe(L)] (P boolean AND O = kappa(2)-P,O-Ar2PC6H4SO2O with Ar = 2-MeOC6H4.; L = C2H6OS) to methyl 2-acetamidoacrylate (MAAA) revealed slight preference for 1,2-insertion over 2,1-insertion (1.0:0.7). In contrast, insertion of electron-deficient 2-(trifluoromethyl)acrylic acid (TFMAA) unveiled selective 2,1-insertion {via [(P boolean AND O)PdC5H6F3O2] (11)1. The unstable intermediate 11 undergoes beta-hydride and beta-fluoride elimination to produce subsequent insertion and elimination products. The identity of elimination products (E/Z)-2-trifluoromethyl)but-2-enoic acid [17(E/Z)] and 2-(difluoromethylene)butanoic acid (13) was fully established by 1-2D NMR spectroscopy. These insertion experiments, taken together with insertion rates, suggest that MAAA and TFMAA. are amenable to insertion. Polymerization of ethylene with MAAA, TFMAA, acetamidoacrylic acid, 2-bromoacrylic acid, dimethyl allylmalonate, and allylmalonic acid was catalyzed by [{P boolean AND O}PdMe(L)] (L = C2H3N) (S.ACN), and the highest incorporation of 11.8% was observed for dimethyl allylmalonate (DMAM). The changes in the surface properties of the copolymers after incorporation of difunctional olefins were evaluated by measuring the water contact angle. Copolymer with highest (11.8% of DMAM) incorporation revealed a reduced water contact angle of 76 degrees. These findings demonstrate that 1,1-disubstituted difunctional olefins are amenable to polymerization, and incorporation of difunctional olefins In polyethylene backbone leads to the production of relatively hydrophilic polyethylene copolymers.1 aGaikwad, Shahaji, R.1 aDeshmukh, Satej, S.1 aKoshti, Vijay, S.1 aPoddar, Suparna1 aGonnade, Rajesh, G.1 aRajamohanan, Pattuparambil, R.1 aChikkali, Samir, H. uhttp://library.ncl.res.in/content/reactivity-difunctional-polar-monomers-and-ethylene-copolymerization-comprehensive-account