RPEP-00004 · 1980The mutant F1 ATPase (an enzyme that helps cells make energy) had only 6 to 9 units of activity per milligram of protein. That is about 10 to 15 times less than the normal version.
The mutant enzyme also broke down faster. After two weeks in the freezer at minus 80 degrees Celsius, it lost about 80% of its activity. The normal enzyme lost none.
When researchers swapped the beta subunit from a normal enzyme into the broken one, activity jumped back up to about 20 units per milligram. That confirmed the problem was in the beta subunit alone. Peptide mapping showed just one peptide fragment differed between the mutant and normal beta subunits.
Kanazawa, H; Horiuchi, Y; Takagi, M; Ishino, Y; Futai, M · In Vitro
RPEP-00020 · 1984Two versions of somatostatin-28 were isolated from anglerfish tissue. Both came from the same gene, but one had a modified amino acid: 5-hydroxylysine at position 23.
Mass spectrometry confirmed the two forms had molecular weights of 3,220 (hydroxylated) and 3,204 (non-hydroxylated). The 16-unit difference matches exactly what adding one oxygen atom would do.
This was the first documented case of a hydroxylated peptide hormone. Before this, hydroxylysine was known almost exclusively from collagen (the protein that gives skin and bones their structure).
Andrews, P C; Hawke, D; Shively, J E; Dixon, J E · In Vitro
RPEP-00027 · 1985Parathymosin alpha is a newly discovered peptide of about 105 amino acid residues, isolated from rat thymus tissue. The first 30 amino acids of its sequence showed 43% structural identity with thymosin alpha 1 and prothymosin alpha.
The structural overlap did not include residues 2 through 9 of thymosin alpha 1. This explained why antibodies targeting that region of thymosin alpha 1 did not recognize parathymosin alpha.
Functionally, parathymosin alpha appeared to regulate prothymosin alpha's ability to protect sensitive mice from Candida albicans (a common fungal infection). This suggests it acts as a modulator of immune protection rather than a direct immune booster.
Haritos, A A; Salvin, S B; Blacher, R; Stein, S; Horecker, B L · In Vitro
RPEP-00056 · 1987The new enzyme immunoassay (EIA) for thymulin achieved a sensitivity of 32.5 ± 5 pg/mL (IC50) with a detection limit of 5 pg/mL. This was more sensitive than previously available radioimmunoassays.
The test was highly specific. It did not cross-react with thymosin alpha 1, thymopoietin II, or TP5 (another thymic peptide). Both the zinc-bound (biologically active) and zinc-free forms of thymulin showed the same immunoreactivity.
Mapping studies showed that the minimum peptide structure needed for detection was the C-terminal portion from lysine-3 to asparagine-9 (7 of the 9 amino acids).
Métreau, E; Pléau, J M; Dardenne, M; Bach, J F; Pradelles, P · In Vitro
RPEP-00061 · 1987The new method combined HPLC (high-performance liquid chromatography) with radioimmunoassay (RIA) to measure opioid peptides in human cerebrospinal fluid, plasma, and tissues.
The key advantage: HPLC first separates beta-endorphin from its precursor beta-lipotropin and from other opioid peptides. Then RIA measures each fraction individually. This eliminates cross-reactivity, where antibodies confuse one peptide for another.
The method uses volatile solvents that evaporate cleanly without interfering with the antibody tests. This was the first combined method that could accurately measure endorphin, enkephalin, and dynorphin families in the same sample.
Preliminary results from chronic pain patients' CSF were presented, demonstrating the method's practical utility.
Venn, R F · In Vitro
RPEP-00072 · 1988Human placental aminopeptidase M completely degraded Met-enkephalin and Leu-enkephalin into their five constituent amino acids. The degradation rate was measured by tracking tyrosine release.
The degradation speed ranked: Met-enkephalin (fastest) > Leu-enkephalin > beta-neoendorphin > dynorphin > beta-endorphin (slowest).
Smaller, simpler peptides were degraded faster than larger, more complex ones. Met-enkephalin (5 amino acids) was destroyed faster than beta-endorphin (31 amino acids).
Furuhashi, M; Mizutani, S; Kurauchi, O; Kasugai, M; Narita, O; Tomoda, Y · In Vitro
RPEP-00187 · 1991Peptides synthesized by azide coupling contained mutagenic contaminants undetectable by HPLC. Switching synthesis methods or using counter-current purification eliminated the problem.
Castellino, S; de Castiglione, R; Forino, R; Galantino, M; Pulci, R · In Vitro
RPEP-00203 · 1991Human serum biotinidase hydrolyzes enkephalins and dynorphin A (<10-mer) with kcat/Km values similar to its biotin substrate biocytin.
Oizumi, J; Hayakawa, K · In Vitro
RPEP-00218 · 1992Column purification validation requires qualification of raw materials, equipment, and process, ideally designed in from the start. Combined with quality control, this ensures batch-to-batch consistency.
· Review
RPEP-00268 · 1993Asp95Asn mutation in delta opioid receptor eliminated selective high-affinity agonist binding while preserving antagonist binding. Single residue determines agonist selectivity.
Kong, H; Raynor, K; Yasuda, K; Moe, S T; Portoghese, P S; Bell, G I; Reisine, T · In Vitro
RPEP-00288 · 1994Hexarelin effectively stimulated growth hormone secretion in both infant and adult rats through a non-GHRH pathway.
Deghenghi, R; Cananzi, M M; Torsello, A; Battisti, C; Muller, E E; Locatelli, V · Animal Study
RPEP-00291 · 1994Orally active dual ACE/NEP inhibitors lowered blood pressure in hypertensive rats through combined angiotensin blockade and natriuretic peptide protection.
Fournié-Zaluski, M C; Coric, P; Turcaud, S; Rousselet, N; Gonzalez, W; Barbe, B; Pham, I; Jullian, N; Michel, J B; Roques, B P · Animal Study
RPEP-00294 · 1994Cecropins, magainin, and melittin disrupted mitochondrial coupling, protein import, and respiration, while PR-39 was nearly inert toward mitochondria.
Hugosson, M; Andreu, D; Boman, H G; Glaser, E · In Vitro
RPEP-00305 · 1994Cloned kappa, delta, and mu opioid receptors showed distinct pharmacological profiles matching decades of predictions from classical pharmacology studies.
Raynor, K; Kong, H; Chen, Y; Yasuda, K; Yu, L; Bell, G I; Reisine, T · In Vitro
RPEP-00314 · 1995ACBC-containing model peptides adopted characteristic stable conformations (helical and extended) that could be leveraged for peptide drug design.
Balaji, V N; Ramnarayan, K; Chan, M F; Rao, S N · In Vitro
RPEP-00331 · 1995Novel backbone-modified GH secretagogues with molecular weight under 500 were the most potent reported, with confirmed anabolic efficacy and a defined bioactive conformation.
McDowell, R S; Elias, K A; Stanley, M S; Burdick, D J; Burnier, J P; Chan, K S; Fairbrother, W J; Hammonds, R G; Ingle, G S; Jacobsen, N E; Mortensen, D L; Rawson, T E; Won, W B; Clark, R G; Somers, T C · Animal Study
RPEP-00333 · 1995Hydrophobic i,i+5 and i,i+8 interactions provide measurable stabilization to alpha-helix structures, with the hydrophobic staple motif contributing to helix nucleation.
Muñoz, V; Serrano, L · In Vitro
RPEP-00334 · 1995The hydrophobic-staple motif (i,i+5 interaction at helix N-terminus) was discovered, validated by NMR, and shown to stabilize alpha-helices and define their N-terminal boundaries.
Muñoz, V; Blanco, F J; Serrano, L · In Vitro
RPEP-00336 · 1995Dynorphin B was processed to leu-enkephalin at a 10,000-fold higher rate than dynorphin A in rat striatal extracts.
Nylander, I; Tan-No, K; Winter, A; Silberring, J · In Vitro
RPEP-00338 · 1995Single HPLC method achieved over 80% recovery of multiple opioid and anti-opioid peptides from human plasma in one analytical run.
Partilla, J S; You, J; Rothman, R B · In Vitro
RPEP-00339 · 1995MK-0677 was characterized as the most potent orally active GH secretagogue, with EC50 of 1.3 nM in vitro, oral efficacy in dogs at 0.125 mg/kg, and confirmed anabolic effects in rodents.
Patchett, A A; Nargund, R P; Tata, J R; Chen, M H; Barakat, K J; Johnston, D B; Cheng, K; Chan, W W; Butler, B; Hickey, G · Animal Study
RPEP-00341 · 1995SQ 28603 potentiated both ANP effects in monkeys (increased plasma ANP, sodium excretion) and BNP effects in hypertensive rats (blood pressure lowering, renal responses).
Seymour, A A; Abboa-Offei, B E; Smith, P L; Mathers, P D; Asaad, M M; Rogers, W L · Animal Study
RPEP-00376 · 1996Pardaxin possesses high antibacterial activity, and engineered variants achieved potent bacterial killing while reducing harmful effects on mammalian cells.
Oren, Z; Shai, Y · In Vitro
RPEP-00380 · 1996A specific high-affinity G-protein-linked receptor for GH secretagogues was identified, operating through a distinct signaling pathway from GHRH.
Pong, S S; Chaung, L Y; Dean, D C; Nargund, R P; Patchett, A A; Smith, R G · In Vitro
RPEP-00392 · 1996NEP inhibition with thiorphan significantly potentiated the blood pressure-lowering, hormonal, and renal effects of all three natriuretic peptides (ANP, BNP, CNP) in hypertensive transgenic rats.
Wegner, M; Ganten, D; Stasch, J P · Animal Study
RPEP-00448 · 1998Sequential backbone modifications of ipamorelin produced smaller peptidomimetic compounds that retained potent GH secretagogue activity, advancing the goal of orally active GH-releasing peptides.
Ankersen, M; Johansen, N L; Madsen, K; Hansen, B S; Raun, K; Nielsen, K K; Thogersen, H; Hansen, T K; Peschke, B; Lau, J; Lundt, B F; Andersen, P H · In Vitro
RPEP-00450 · 1998Phenyl piperazine-based peptidomimetics were identified as potent, orally active GH secretagogues by mimicking privileged structural motifs from known GH-releasing compounds.
Barakat, K J; Cheng, K; Chan, W W; Butler, B S; Jacks, T M; Schleim, K D; Hora, D F; Hickey, G J; Smith, R G; Patchett, A A; Nargund, R P · In Vitro
RPEP-00463 · 1998Thymosin alpha-1 adopts a structured conformation with a beta-turn (residues 5-8) and alpha helix (residues 17-24) in membrane-like environments, suggesting this shape change is required for immune cell activation.
Grottesi, A; Sette, M; Palamara, T; Rotilio, G; Garaci, E; Paci, M · In Vitro
RPEP-00468 · 1998The cecropin A-magainin 2 hybrid peptide disrupts membranes via a two-step mechanism, and leucine substitution analogs showed enhanced membrane disruption and antitumor activity with preserved low hemolytic toxicity.
Kang, J H; Shin, S Y; Jang, S Y; Lee, M K; Hahm, K S · In Vitro
RPEP-00510 · 1999Solid-state NMR studies showed antimicrobial peptides adopt amphipathic helical structures oriented parallel to bacterial membrane surfaces, providing a structural basis for their selective membrane disruption mechanism.
Bechinger, B · Review
RPEP-00518 · 1999Sixteen novel cyclotides were identified from three plant species, all sharing the cyclic cystine knot motif that confers exceptional thermal, chemical, and enzymatic stability, with diverse bioactivities including antimicrobial and anti-HIV effects.
Craik, D J; Daly, N L; Bond, T; Waine, C · In Vitro
RPEP-00519 · 1999Circulin A's 3D structure reveals a cyclic cystine knot fold with exposed hydrophobic and positively charged surface patches, providing a structural basis for its membrane-disrupting anti-HIV activity.
Daly, N L; Koltay, A; Gustafson, K R; Boyd, M R; Casas-Finet, J R; Craik, D J · In Vitro
RPEP-00520 · 1999Antimicrobial peptide selectivity follows a balance: moderate hydrophobicity and amphipathicity maximize bacterial killing with minimal human cell toxicity, while excessive hydrophobicity increases toxicity without improving antibacterial activity.
Dathe, M; Wieprecht, T · Review
RPEP-00539 · 1999High-resolution crystal structures of seven macrocyclic HIV protease inhibitors revealed specific binding interactions, demonstrating how cyclic peptide scaffolds can achieve potent enzyme inhibition with improved drug properties.
Martin, J L; Begun, J; Schindeler, A; Wickramasinghe, W A; Alewood, D; Alewood, P F; Bergman, D A; Brinkworth, R I; Abbenante, G; March, D R; Reid, R C; Fairlie, D P · In Vitro
RPEP-00548 · 1999Structural comparison revealed the cecropin-magainin hybrid has a bent helix with different hydrophobic surface distribution than the cecropin-melittin hybrid, explaining its superior bacterial selectivity and lower human cell toxicity.
Oh, D; Shin, S Y; Kang, J H; Hahm, K S; Kim, K L; Kim, Y · In Vitro
RPEP-00557 · 1999Structure-activity analysis identified the amphipathic helix hydrophobic face as essential for antibacterial activity, tryptophan as important for antitumor activity, and specific substitutions that separate antimicrobial potency from hemolytic toxicity.
Shin, S Y; Kang, J H; Hahm, K S · In Vitro
RPEP-00567 · 1999Macrocyclic cystine-knot peptides showed antimicrobial activity requiring both the intact circular backbone and disulfide knot; disrupting either eliminated structure and biological activity.
Tam, J P; Lu, Y A; Yang, J L; Chiu, K W · In Vitro
RPEP-00578 · 2000The minimal active ghrelin fragment is the first 4 amino acids (GSSF) with octanoyl modification on Ser3; the fatty acid modification is essential while most of the 28-residue chain is dispensable for receptor activation.
Bednarek, M A; Feighner, S D; Pong, S S; McKee, K K; Hreniuk, D L; Silva, M V; Warren, V A; Howard, A D; Van Der Ploeg, L H; Heck, J V · In Vitro
RPEP-00589 · 2000Acyclic permutants of kalata B1 folded into native-like cystine knot structures without the circular backbone, but backbone cyclization was required for full biological activity and optimal structural stability.
Daly, N L; Craik, D J · In Vitro
RPEP-00592 · 2000Three macrocyclic trypsin inhibitors (MCoTI-I, -II, -III) from Momordica cochinchinensis are the smallest known naturally cyclic peptides, with atypical backbone cyclization and potent trypsin inhibition.
Hernandez, J F; Gagnon, J; Chiche, L; Nguyen, T M; Andrieu, J P; Heitz, A; Trinh Hong, T; Pham, T T; Le Nguyen, D · In Vitro
RPEP-00593 · 2000Self-assembling peptide scaffolds supported extensive neurite outgrowth and formation of active, functional synapses, demonstrating programmable peptide-based materials for neural regeneration.
Holmes, T C; de Lacalle, S; Su, X; Liu, G; Rich, A; Zhang, S · In Vitro
RPEP-00612 · 2000Hybrid CCK-A agonist peptides combining structural features of hexapeptide and tetrapeptide classes showed potent receptor binding and selectivity, advancing design of satiety-inducing peptide drugs for obesity.
Pierson, M E; Comstock, J M; Simmons, R D; Julien, R; Kaiser, F; Rosamond, J D · In Vitro
RPEP-00631 · 2000Opioid peptide gene expression (prodynorphin, proenkephalin) preceded cardiac transcription factor activation (GATA-4, Nkx-2.5) during cardiogenesis in embryonic stem cells, suggesting opioid peptides prime heart cell development.
Ventura, C; Maioli, M · In Vitro
RPEP-00666 · 2001NN703-ipamorelin hybrid GH secretagogues showed low nanomolar in vitro potency in pituitary cell assays and effective GH release in pigs in vivo, validating the hybrid design approach.
Hansen, T K; Ankersen, M; Raun, K; Hansen, B S · In Vitro
RPEP-00676 · 2001Optimized ghrelin tetrapeptide derivatives showed structural similarity to synthetic peptidyl GH secretagogues like GHRP-1, demonstrating convergent molecular solutions between the natural ligand and designed drugs.
Matsumoto, M; Kitajima, Y; Iwanami, T; Hayashi, Y; Tanaka, S; Minamitake, Y; Hosoda, H; Kojima, M; Matsuo, H; Kangawa, K · In Vitro
RPEP-00683 · 2001SM-130686, a structurally novel oxindole GH secretagogue, showed potent in-vitro and in-vivo GH-releasing activity, increased IGF-1 and body weight in rats, and was orally active, demonstrating a new chemical class for GHS-R targeting.
Nagamine, J; Nagata, R; Seki, H; Nomura-Akimaru, N; Ueki, Y; Kumagai, K; Taiji, M; Noguchi, H · Animal Study
RPEP-00690 · 2001Spiro(indoline-piperidine) small molecules mimicking ghrelin's N-terminal active core showed potent GHS-R binding and functional calcium signaling activation, validating small-molecule ghrelin mimicry.
Palucki, B L; Feighner, S D; Pong, S; McKee, K K; Hreniuk, D L; Tan, C; Howard, A D; Van der Ploeg, L H; Patchett, A A; Nargund, R P · In Vitro
RPEP-00698 · 2001The octanoyl modification on Ser3 stabilizes a turn structure in ghrelin's N-terminal active core (first 5 residues), explaining its essential role in receptor binding and activation at the structural level.
Silva Elipe, M V; Bednarek, M A; Gao, Y D · In Vitro
RPEP-00721 · 2002Cyclotides combine exceptional structural stability (thermal, enzymatic, chemical resistance) with sequence-tolerant scaffolding capability, enabling design of stable peptide drugs through grafting bioactive sequences into the cyclotide framework.
Craik, David J; Simonsen, Shane; Daly, Norelle L · Review
RPEP-00740 · 2002Self-assembling peptide hydrogels maintained chondrocyte phenotype, supported cell division, and promoted extracellular matrix production (GAG, type II collagen), demonstrating functional cartilage tissue formation in a peptide scaffold.
Kisiday, J; Jin, M; Kurz, B; Hung, H; Semino, C; Zhang, S; Grodzinsky, A J · In Vitro