Recent Research in Science and Technology 2010, 2(1): 78–82 ISSN: 2076-5061 www.recent-science.com BIOTECHNOLOGY RHODAMINE-B LABELED PEPTIDE HORMONE EVALUATION BY THIN LAYER CHROMATOGRAPHY Felsi Priyadarsini, Aniket Kumar, A. Babu Vimalanathan, Manoj G. Tyagi  Department of Pharmacology, Christian Medical College, Vellore 632002, Tamilnadu, India Abstract A novel thin layer chromatographic procedure was devised to evaluate the activity of rhodamine-B tagged peptide hormone such as vasopressin & octreotide. Peptide hormones viz. octreotide and vasopressin were added with rhodamine-B (0.2 ml of concentration 2.5mg/ml) and were estimated through thin layer chromatography (TLC) in a concentration and time dependent manner i.e. 25μg, 50μg for 30 & 60 minutes and 4.8μg, 9.6μg for 30 & 60 minutes respectively. The solvent medium used was a mixture of butanol, acetic acid and water in a ratio of 4:1:1. Stationary phase used in this experiment was Silica gel mixed with an inert binder like calcium sulphate and water. Different peptides travel at different rates due to the differences in their attraction to the stationary phase and because of difference in solubility in the solvent. The plates were made to visualize under a UV detector and respective Rf values were calculated. Results showed that rhodamine-B tagged peptides were well seen under UV detector as well as with naked eyes and is an efficacious marker when compared with other developing systems such as ninhydrin, iodine spray etc. Key Words: TLC, vasopressin, octreotide, Rf, GPCR.  Corresponding Author, Email: tyagi257@yahoo.in Introduction G protein coupled receptors (GPCR) binding ligands are extensively studied as GPCRs represent the single largest molecular target of therapeutic drugs currently on the market, but is also the most common target in high- throughput screening (HTS) assays for identifying potential new drug candidates 1 . We chose two candidate hormones i.e vasopressin (9 amino acid) and Octreotide (8 aminoacid) almost similar in size for this study. Both these hormones bind to their respective GPCR and their analogues are being studied for novel therapeutic purposes. Vasopressin is a human hormone that is released when the body is low on water; it causes the kidneys to conserve water, but not salt, by concentrating the urine and reducing urine volume. It also raises blood pressure by inducing moderate vasoconstriction. Vasopressin is a peptide hormone. It is derived from a preprohormone precursor that is synthesized in the hypothalamus, from which it is liberated during transport to the posterior pituitary. Most of it is stored in the posterior part of the pituitary gland to be released into the blood stream; some of it is also released directly into the brain.The vasopressins are peptides consisting of nine amino acids (nonapeptides) 2 . The amino acid sequence of arginine vasopressin is Cys-Tyr-Phe-Gln-Asn-Cys-Pro- Arg-Gly, with the cysteine residues forming a sulfur bridge. The structure of oxytocin another posterior pituitary hormone is very similar to that of the vasopressins: it is also a nonapeptide with a sulfur bridge and its amino acid sequence differs at only two positions. On the other hand, Octreotide is the acetate salt of a cyclic octapeptide. It is a long acting octapeptide with pharmacologic properties mimicking those of the natural hormone somatostatin 3 .Octreotide is known chemically as L-Cysteinamide, D- phenylalanyl-L-cysteinyl-L-phenylalanyl-D-tryptophyl-L- lysyl-L-threonyl-N- [2-hydroxy-1-(hydroxylmethyl) propyl], cyclic(2→7)disulfide;[R-(R*,R*)].It is commercially available as Sandostatin LAR® Depot (octreotide acetate for injectable suspension) and is available in a vial containing the sterile drug product, which when mixed with diluent, becomes a suspension that is given as a monthly intragluteal injection. The octreotide is uniformly distributed within the microspheres which are made of a biodegradable glucose star polymer, D,L-lactic and glycolic acids copolymer. Sterile mannitol is added to the microspheres to improve suspendibility. Somatostatin is a 14 amino acid hormone. Octreotide is a derivative of somatostatin with a much longer half life. Both have the same therapeutic properties. The molecular weight of octreotide is 1019 daltons. It is used for the treatment of oesophageal varices. Most of the HTS procedures are still presently based on radioligand binding competition assays. Fluorescence approaches, based on the development of fluorescent ligands, offer a