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Padmanabhan Balaram - One of the best experts on this subject based on the ideXlab platform.
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directing peptide conformation with centrally positioned pre organized dipeptide segments studies of a 12 residue helix and β hairpin
Amino Acids, 2015Co-Authors: Siddappa Chandrappa, M Madhusudana B Reddy, Rajesh Sonti, Krishnayan Basuroy, Srinivasarao Raghothama, Padmanabhan BalaramAbstract:Secondary structure formation in oligopeptides can be induced by short nucleating segments with a high propensity to form hydrogen bonded turn conformations. Type I/III turns facilitate helical folding while type II'/I' turns favour hairpin formation. This principle is experimentally verified by studies of two designed dodecapeptides, Boc-Val-Phe-Leu-Phe-Val-Aib-Aib-Val-Phe-Leu-Phe-Val-OMe 1 and Boc-Val-Phe-Leu-Phe-Val- (D) Pro- (L) Pro-Val-Phe-Leu-Phe-Val-OMe 2. The N- and C-terminal flanking pentapeptide sequences in both cases are identical. Peptide 1 adopts a largely alpha-helical conformation in crystals, with a small 3(10) helical segment at the N-terminus. The overall helical fold is maintained in methanol solution as evidenced by NMR studies. Peptide 2 adopts an antiparallel beta-hairpin conformation stabilized by 6 interstrand hydrogen bonds. Key nuclear Overhauser effects (NOEs) provide evidence for the antiparallel beta-hairpin structure. Aromatic proton chemical shifts provide a clear distinction between the conformation of peptides 1 (helical) and 2 (beta-hairpin). The proximity of facing aromatic residues positioned at non-hydrogen bonding positions in the hairpin results in extensively ring current shifted proton resonances in peptide 2.
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aromatic interactions in model peptide β hairpins ring current effects on proton chemical shifts
Biopolymers, 2012Co-Authors: Appavu Rajagopal, Srinivasarao Raghothama, Subrayashastry Aravinda, Narayanaswamy Shamala, Padmanabhan BalaramAbstract:Crystal structures of eight peptide β-hairpins in the sequence Boc-Leu-Phe-Val-Xxx-Yyy-Leu-Phe-Val-OMe revealed that the Phe(2) and Phe(7) aromatic rings are in close spacial proximity, with the centroid–centroid distance (Rcen) of 4.4–5.4 A between the two phenyl rings. Proton NMR spectra in chloroform and methanol solution reveal a significant upfield shift of the Phe(7) Cδ,δ′H2 protons (6.65–7.04 ppm). Specific assignments of the aromatic protons have been carried out in the peptide Boc-Leu-Phe-Val-DPro-LPro-Leu-Phe-Val-OMe (6). The anticipated ring current shifts have been estimated from the aromatic ring geometrics observed in crystals for all eight peptides. Only one of the Cδ,δ′H proton lies in the shielding zone with rapid ring flipping, resulting in averaging between the two extreme chemical shifts. An approximate estimate of the population of conformations, which resemble crystal state orientation, may be obtained. Key nuclear Overhauser effects (NOEs) between facing Phe side chains provide support for close similarity between the solid state and solution conformation. Temperature dependence of aromatic ring proton chemical shift and line widths for peptide 6 (Boc-Leu-Phe-Val-DPro-LPro-Leu-Phe-Val-OMe) and the control peptide Boc-Leu-Val-Val-DPro-Gly-Leu-Phe-Val-OMe establish an enhanced barrier to ring flipping when the two Phe rings are in proximity. Modeling studies suggest that small, conformational adjustment about CαCβ (χ1) and CβCγ (χ2) bonds of both the Phe residues may be required in order to permit unhindered, uncorrelated flipping of both the Phe rings. The maintenance of the specific aromatic ring orientation in organic solvents provides evidence for significant stabilizing interaction. © 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 98: 185–194, 2012.
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characterization of bent helical conformations in polymorphic forms of a designed 18 residue peptide containing a central gly pro segment
Biopolymers, 2012Co-Authors: Subrayashastry Aravinda, Isabella L Karle, Narayanaswamy Shamala, Padmanabhan BalaramAbstract:An 18-residue sequence Boc-Aib-Val-Ala-Leu-Aib-Val-Ala-Leu-Gly-Pro-Val-Ala-Leu-Aib-Val-Ala-Leu-Aib-OMe (UK18) was designed to examine the effect of introducing a Gly-Pro segment into the middle of a potentially helical peptide. The crystal structures of two polymorphic forms yielded a view of the conformation of three independent molecules. Form 1 (space group P212121, a = 14.620A; b = 26.506A, c = 28.858A, Z = 4) has one molecule in the asymmetric unit, with one cocrystallized water molecule. Form 2 (space group P212121, a = 9.696A; b = 19.641A, c = 114.31A, Z = 8) has two molecules in the asymmetric unit with four cocrystallized water molecules. In Form 1, residues 1 to 18 adopt ϕ,ψ values that lie in the right-handed helical (αR) region of the Ramachandran map. Two residues, Leu (8) (ϕ = −92.0°, ψ = −7.5°) and Leu (17) (ϕ = −94.7°, ψ = −1.7°) adopt conformations that deviate significantly from helical values. In Form 2, molecule A, residues 2 to 16 lie in the αR region of ϕ,ψ space, with Leu (8) (ϕ = −94.9°, ψ = −2.9°) deviating significantly from helical values. Aib (1) and Aib (18) adopt left-handed (αL) helical conformation. Significant distortion is observed at Leu (17) (ϕ = −121.3°, ψ = −31.3°). Molecule B, Form 2, adopts a right-handed helix over residues 1 to 17. In all three molecules, a distinct bend in the helix is observed, with the bend angle values varying from 40.8° to 58.9°. © 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 98: 76–86, 2012.
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tuning the β turn segment in designed peptide β hairpins construction of a stable type i β turn nucleus and hairpin helix transition promoting segments
Biopolymers, 2007Co-Authors: Rajkishor Rai, Srinivasarao Raghothama, Rajagopalan Sridharan, Padmanabhan BalaramAbstract:Designed octapeptides Boc-Leu-Val-Val-Aib-$^DXxx$-Leu-Val-Val-OMe $(^DXxx=^DAla, 3a; ^DVal, 3c$ and $^DPro, 5a)$ and Boc-Leu-Phe-Val-Aib-$^DAla$-Leu-Phe-Val-OMe (3b) have been investigated to construct models of a stable type I' $\beta$-turn nucleated hairpin and to generate systems for investigating helix–hairpin conformational transitions. Peptide 5a, which contains a central $Aib-^D$ Pro segment, is shown to adopt a stable type I' $\beta$-turn nucleated hairpin structure, stabilized by four cross-strand hydrogen bonds. The stability of the structure in diverse solvents is established by the observation of all diagnostic NOEs expected in a $\beta$-hairpin conformation. Replacement of $^DPro5$ by $^DAla/^DVal (3a-c)$ results in sequences that form $\beta$-hairpins in hydrogen bonding solvents like $CD_3OH$ and $DMSO-d_6$. However, in $CDCl_3$ evidence for population of helical conformations is obtained. Peptide 6b (Boc-Leu-Phe-Val-Aib-Aib-Leu-Phe-Val-OMe), which contains a centrally positioned Aib-Aib segment, provides a clear example of a system, which exhibits a helical conformation in $CDCl_3$ and a significant population of both helices and hairpins in $CD_3OH$ and $DMSO-d_6$. The coexistence of multiple conformations is established by the simultaneous observation of diagnostic NOEs. Control over stereochemistry of the central $\beta$-turn permits generation of models for robust $\beta$-hairpins and also for the construction of systems that may be used to probe helix–hairpin conformational transitions.
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designed beta hairpin peptides with defined tight turn stereochemistry
Biopolymers, 2001Co-Authors: G A Naganagowda, Isabella L Karle, Padmanabhan BalaramAbstract:The conformational analysis of two synthetic octapeptides, Boc–Leu–Val–Val–D-Pro–L-Ala–Leu–Val–Val–OMe (1) and Boc–Leu–Val–Val–D-Pro–D-Ala–Leu–Val–Val–OMe (2) has been carried out in order to investigate the effect of beta-turn stereochemistry on designed beta-hairpin structures. Five hundred megahertz 1HNMR studies establish that both peptides 1 and 2 adopt predominantly beta-hairpin conformations in methanol solution. Specific nuclear Overhauser effects provide evidence for a type II’ beta-turn conformation for the D-Pro–L-Ala segment in 1, while the NMR data suggest that the type I’ D-Pro–D-Ala b-turn conformation predominates in peptide 2. Evidence for a minor conformation in peptide 2, in slow exchange on the NMR time scale, is also presented. Interstrand registry is demonstrated in both peptides 1 and 2. The crystal structure of 1 reveals two independent molecules in the crystallographic asymmetric unit, both of which adopt beta-hairpin conformations nucleated by D-Pro–Lala type II’ beta-turns and are stabilized by three cross-strand hydrogen bonds. CD spectra for peptides and 2 show marked differences, presumably as a consequence of the superposition of spectral bands arising from both beta-turn and beta-strand conformations.
Runguang Zhang - One of the best experts on this subject based on the ideXlab platform.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Yan Li, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
Yajun Zheng - One of the best experts on this subject based on the ideXlab platform.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Yan Li, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
Xiaohui Ruan - One of the best experts on this subject based on the ideXlab platform.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Yan Li, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
Youlin Zhang - One of the best experts on this subject based on the ideXlab platform.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Yan Li, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
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purification characterization synthesis in vitro ace inhibition and in vivo antihypertensive activity of bioactive peptides derived from oil palm kernel glutelin 2 hydrolysates
Journal of Functional Foods, 2017Co-Authors: Yajun Zheng, Youlin Zhang, Xiaohui Ruan, Runguang ZhangAbstract:Abstract Palm kernel expeller glutelin-2 hydrolysates (PKEGH) with high ACE-inhibitory activity (80.24%) were obtained by the sequential digestion with alcalase, flavourzyme, pepsin and trypsin assisted by high pressure pretreatment. PKEGH were separated by ultrafiltration, Sephadex G-25 gel chromatography and RP-HPLC. Finally four novel ACE-inhibitory peptides (Ala-Asp-Val-Phe-Asn-Pro-Arg, Val-Val-Leu-Tyr-Lys, Leu-Pro-Ile-Leu-Arg and Val-Ile-Glu-Pro-Arg) were identified, of which Val-Val-Leu-Tyr-Lys showed the highest activity (IC50: 533.9 μM). All the four peptides exhibited potent non-competitive ACE inhibition and relatively good stability against gastrointestinal enzymes digestion. Moreover, these peptides significantly lowered the endothelin-1 content in EA.hy926 cells without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, the PKEGH and individual ACE-inhibitory peptides identified from it showed chronic antihypertensive effects in spontaneously hypertensive rats after several days/weeks administration. Result showed that Palm kernel expeller glutelin-2 could be effectively converted to produce ACE-inhibitory or antihypertensive peptides.
