1. Labeling peptides with rhenium-188
L Meléndez-Alafort, G Ferro-Flores, C Arteaga-Murphy, M Pedraza-López, M A González-Zavala, J I Tendilla, L García-Salinas Int J Pharm. 1999 May 25;182(2):165-72. doi: 10.1016/s0378-5173(99)00054-x.
A direct labeling technique via EHDP for the preparation of 188Re-somatostatin analogue peptide beta-(2-naphthyl)-D-Ala-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-amide complex was developed. The influence of reaction conditions such as pH, temperature, weak ligand concentration and stannous chloride concentration were investigated. Methods of analysis were also established permitting identification of radiochemical impurities which may be present in the radiopharmaceutical solution. Results showed that under the procedure reported herein 188Re-peptide complex can be prepared with a radiochemical purity of 90% and a specific activity up to 1.8 GBq mg-1 without radiolytic degradation of the product.
2. Structural study of melanocortin peptides by fluorescence spectroscopy: identification of beta-(2-naphthyl)-D-alanine as a fluorescent probe
Roberto M Fernandez, Amando S Ito, Helgi B Schiöth, M Teresa Lamy Biochim Biophys Acta. 2003 Sep 8;1623(1):13-20. doi: 10.1016/s0304-4165(03)00152-1.
Several cyclic disulfide alpha-melanocyte stimulating hormone (alpha-MSH) analogues containing the aromatic fluorescent amino acid beta-(2-naphthyl)-D-alanine (D-Nal) have high affinity and selectivity for the melanocortin (MC)-4 receptor. Considering the possible relevant role played by the lipid phase in the peptide-receptor interaction, the structures of two cyclic alpha-MSH analogues, containing both Trp and D-Nal fluorophores, were investigated by steady-state and time-resolved fluorescence spectroscopy, in aqueous solution and in the presence of dimyristoyl phosphatidylglycerol (DMPG) vesicles, and compared with that of the natural peptide. The amino acid D-Nal gives a unique de-excitation fluorescence profile, with an excited state lifetime much longer than those of Trp, allowing good distinction between the two fluorophores. The cyclic analogues' aqueous structures seem to be adequate for membrane penetration, as Trp fluorescence indicates that, in both aqueous and lipid media, the Trp environment in the cyclic peptides is similar to that of alpha-MSH when incorporated in lipid bilayers. Trp, in the cyclic analogues, seems to penetrate deeper in the bilayer than in the native peptide. The amino acid D-Nal was also found to penetrate deep into the lipid bilayer, having its excited-state lifetime drastically changed from aqueous solution to lipid medium. The present work shows that D-Nal may serve as a fluorescent probe for studies of MC peptides and suggests that the high affinity and selectivity of the cyclic peptides to the MC4 membrane receptor could be related to their deeper penetration into the bilayer core.
3. Synthesis and microbiological activities of beta-(1-chloro-2-naphthyl) alanine and beta-(1-bromo-2-naphthyl) alanine
T J McCord, R N Watson, C E DuBose, K L Hulme, A L Davis J Med Chem. 1976 Mar;19(3):429-30. doi: 10.1021/jm00225a020.
beta-(1-Chloro-2-naphthyl)alanine and beta-(1-bromo-2-naphthyl) alanine were synthesized by ammonolysis of the corresponding alpha, 1-dihalo-2-naphthalenepropanoic acids derived from 1-nitro-2-naphthylamine by diazotization and condensation with acrylic acid in the presence of cuprous halides. The two analogs as well as the previously reported beta-(2-naphthyl)alanine and beta-(1-naphthyl)alanine were studied as growth inhibitors of Escherichia coli 9723, Leuconostoc dextranicum 8086, and Lactobacillus plantarum 8014. In general, the chloro and bromo analogs were more effective than the unsubstituted naphthylalanines as growth inhibitors of the three microorganisms studied.
