1.Methionine residue acts as a prooxidant in the •OH-induced oxidation of enkephalins.
Mozziconacci O1, Mirkowski J, Rusconi F, Kciuk G, Wisniowski PB, Bobrowski K, Houée-Levin C. J Phys Chem B. 2012 Oct 18;116(41):12460-72. doi: 10.1021/jp307043q. Epub 2012 Oct 9.
Enkephalins are bioactive pentapeptides (Tyr-Gly-Gly-Phe-Leu (Leu-enk) and Tyr-Gly-Gly-Phe-Met (Met-enk)) produced while an organism is under mental and/or physical stress. In the course of their biological action they are exposed to reactive oxygen and nitrogen species. We have reinvestigated the reactions of (•)OH radicals toward these peptides in order to elucidate the oxidation mechanisms and the final products. Nanosecond pulse radiolysis was used to obtain the spectra of the reaction intermediates and their kinetics. Additional insight into details of the oxidation mechanism was gained by identification of main final products by means of UV-vis spectrophotometry, HPLC coupled with fluorescence spectroscopy, and mass spectrometry. The key processes are different in both peptides. In Leu-enk, the first step is an (•)OH radical addition to the aromatic rings of Tyr and Phe residues that leads to hydroxylated residues, dihydroxyphenylalanine (DOPA) from Tyr and tyrosine isomers from Phe, respectively.
2.N-terminal guanidinylation of TIPP (Tyr-Tic-Phe-Phe) peptides results in major changes of the opioid activity profile.
Weltrowska G1, Nguyen TM, Chung NN, Wilkes BC, Schiller PW. Bioorg Med Chem Lett. 2013 Sep 15;23(18):5082-5. doi: 10.1016/j.bmcl.2013.07.036. Epub 2013 Jul 23.
Derivatives of peptides of the TIPP (Tyr-Tic-Phe-Phe; Tic=1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) family containing a guanidino (Guan) function in place of the N-terminal amino group were synthesized in an effort to improve their blood-brain barrier permeability. Unexpectedly, N-terminal amidination significantly altered the in vitro opioid activity profiles. Guan-analogues of TIPP-related δ opioid antagonists showed δ partial agonist or mixed δ partial agonist/μ partial agonist activity. Guanidinylation of the mixed μ agonist/δ antagonists H-Dmt-Tic-Phe-Phe-NH2 (DIPP-NH2) and H-Dmt-TicΨ[CH2NH]Phe-Phe-NH2 (DIPP-NH2[Ψ]) converted them to mixed μ agonist/δ agonists. A docking study revealed distinct positioning of DIPP-NH2 and Guan-DIPP-NH2 in the δ receptor binding site. Lys(3)-analogues of DIPP-NH2 and DIPP-NH2[Ψ] (guanidinylated or non-guanidinylated) turned out to be mixed μ/κ agonists with δ antagonist-, δ partial agonist- or δ full agonist activity.
3.Synthesis of hemopressin peptides by classical solution phase fragment condensation.
Reddy PA1, Jones ST, Lewin AH, Carroll FI. Int J Pept. 2012;2012:186034. doi: 10.1155/2012/186034. Epub 2012 Nov 27.
A fragment condensation solution phase assembly of the naturally occurring CB(1) inverse agonist nonapeptides, Pro-Val-Asn-Phe-Lys-Phe/Leu-Leu-Ser-His-OH (hemopressins), and two other homologues: N-terminal 2-amino acid (dipeptide) extended undecapeptide, Val-Asp-Pro-Val-Asn-Phe-Lys-Leu-Leu-Ser-His-OH, and three-amino acid (tripeptide) extended dodecapeptide, Arg-Val-Asp-Pro-Val-Asn-Phe-Lys-Leu-Leu-Ser-His-OH, both CB(1) agonists, is reported.
4.A G protein-coupled receptor (GPCR) in red: live cell imaging of the kappa opioid receptor-tdTomato fusion protein (KOPR-tdT) in neuronal cells.
Huang P1, Chiu YT, Chen C, Wang Y, Liu-Chen LY. J Pharmacol Toxicol Methods. 2013 Nov-Dec;68(3):340-5. doi: 10.1016/j.vascn.2013.07.002. Epub 2013 Jul 12.
INTRODUCTION: In contrast to green fluorescent protein and variants (GFPs), red fluorescent proteins (RFPs) have rarely been employed for the generation of GPCR fusion proteins, likely because of formation of aggregates and cell toxicity of some RFPs. Among all the RFPs, tdTomato (tdT), one of the non-aggregating RFP, has the highest brightness score (about 3 times that of eGFP) and unsurpassed photostability.
