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For use as a calibration standard for mass spectrometry
Analytical work in the field of peptide and protein chemistry, especially the elucidation of amino acid sequences involves primarily the use of proteolytic enzymes as well as the application of selective chemical cleavage or stepwise degradation methods to break down the amino chain of the product under investigation. The use of such methods demands at first precise knowledge of details of the special technique. The Model Peptide system offered enables intensive study of such methods. The whole kit consists of a unique, novel combination of peptides and the appropriate free amino acids having the following structures:1. The hexapeptide Model Substrate (MS): H-LEU-TRP-MET-ARG-PHE-ALA-OH2. A series of nine model peptide standards (Fragments of MS):a.H-LEU-TRP-OHb.H-LEU-TRP-MET-OHc.H-LEU-TRP-MET-ARG-OHd.H-LEU-TRP-MET-ARG-PHE-ALA-OHe.H-MET-ARG-PHE-ALA-OHf.H-MET-ARG-PHE-OHg.H-ARG-PHE-ALA-OHh.H-PHE-ALA-OHj.H-ARG-PHE-OH3. The six free amino acids of which the model substrate is composed: LEU;TRP;MET;ARG;PHE;ALAThe Model Substrate was designed in a way that it can be cleaved by the following procedures:ENZYMATIC DEGRADATION1. The highly specific enzyme Trypsin, cleaves the peptide bond between the arginine and the phenylalanine residues of MS yielding fragments C and H. 2. Chymotrypsin cleavage occurs preferably at the bonds between the tryptophan and methionine residues with formation of fragment A, free alanine and fragment F, if complete hydrolysis is forced. In case of incomplete cleavage, fragments D and E can also be observed under certain conditions. 3. Aminopeptidase M splits through the entire sequence starting at the N-terminus by subsequent removal of leucine, tryptophan and so forth. 4. Leucineaminopeptidase also removes the amino acids stepwise in the same manner, however with different rates. 5. Carboxypeptidase A starts hydrolysis at the C-terminus and splits alanine and phenyalanine to form fragments D and C. 6. Carboxypeptidase B continues this degradation by removal of arginine from fragment C to yield fragment B. 7. Pronase, which was proved to consist of a mixture of aminopeptidases, carboxypeptidases and rather unspecific endopeptidases, cleaves the substrate in different ways depending on the enzyme function being used. CHEMICAL CLEAVAGE 1. Cyanogen bromide cleaves the peptide bond between the methionine and arginine residues specifically with formation of a modified fragment B (methionine is converted to homoserine lactone) and of fragment G. 2. N-Bromosuccinimide selectively splits the bond between the tryptophan and methionine residues producing fragment E and a modified fragment A (tryptophan is oxidized to dioxoIndole alanine) 3. Reaction with phenylisothiocyanate at the N-terminus and subsequent removal of leucine as phenylthiohydantoin, well known as Edman degradation, can be repeated thus degrading the entire sequence. ( see our Pth amino acids). In addition to each Edman degradation step any remaining fragment (as well as the uncleaved model substrate or fragments E, G and H) may be used to study modern methods to determine N-terminal amino acids, such as the widely used Dansyl technique and the Edman-Dansyl combination procedure. The whole model peptide system may therefore be used to study, test and train all methods describes. It might be useful for students as well as for those research workers who start using any of these standard procedures. In addition to the educational applicability, the model peptide system offers a wide use for any modern research work, whenever new enzymatic or chemical methods of peptide chain degradation are to be studied or examined. Last but not least the system represents a very sensitive tool for advanced and sophisticated research workers during the examination of the specificity of newly formed proteolytic enzymes or the search for such enzymes in all kinds of biological systems. EXPERIMENTALIn order to study any of the above mentioned reactions the model substrate (MS) is cleaved and the fragments obtained are identified qualitatively or semi-qualitatively by means of thin layer chromatography or electrophoresis in comparison to the respective authentic model peptide standards (A to J) and amino acids. For quantitative studies the exact amount of fragments may be determined by ion exchange chromatography using well established equipment such as automatic amino acid analyzers adjusted for peptide separations. In typical examples the separation of (MS) and of all standards by means of thin layer chromatography in two systems is demonstrated as well as the enzymatic cleavage of (MS) by trypsin. a) Thin Layer Chromatography: About 50 ug of (MS) and of each peptide standard are dissolved in 0.1 ml. methanol-water mixture (1:1;v/v). 10 ul of each solution are then pipetted on a thin layer plate coated with silica-gel. In two solvent systems, separation is possible as indicated in fig.1
b) Enzymatic cleavage by trypsin: The digestion of (MS) by trypsin can be carried out at 25oC in 0.2M ammonium acetate buffer, adjusted to pH 7.0 by addition of acetic acid. 0.5 mgs. of (MS) are dissolved in 0.1 ml. MeOH and 1.0 ml. buffer solution and a solution of 0.02 mg. of trypsin in 1 ml. buffer is added. The incubation mixture is kept for four hours at 25oC; hereafter enzymatic degradation is stopped by addition of 0.5 ml. glacial acetic acid and the mixture is lyophilized to remove the volatile buffer. The remaining residue is dissolved in 0.5 ml. methanol/water mixture (1:1;v/v) and 10 ul of this solution is submitted to thin layer chromatography with the set of standards as described under (a).
12-4350-02H-LEU-TRP-MET-ARG-PHE-ALA (MS)50 mg.12-4351-02H-LEU-TRP (fragment A)50 mg.12-4352-02H-LEU-TRP-MET (fragment B)50 mg.12-4353-02H-LEU-TRP-MET-ARG (fragment C)50 mg.12-4354-02H-LEU-MET-MET-ARG-PHE (fragment D)50 mg.13-4794-02H-MET-ARG-PHE-ALA (fragment E)50 mg.13-4811-02H-MET-ARG-PHE (fragment F)50 mg.01-0268-02H-ARG-PHE-ALA (fragment G)50 mg.16-5916-02H-PHE-ALA (fragment H)50 mg.01-0315-02H-ARG-PHE (fragment J)50 mg.or items may be ordered as a kit:
13-4879-12MODEL PEPTIDE SUBSTRATE KIT:50 mgs. of MS plus 10 mgs. of each of the standards and 1 gm. each of Leu;Trp;Met;Arg;Phe;Ala13-4795-13MODEL PEPTIDE STANDARDS (fragments only) KIT:50 mgs. of each of the nine standards
Dimethyl-B-Propiothetin (DMPT) (DMSP)DMPT is an algae metabolite. It reacts with cell-permeable I' to produce Mel and OH' to form ME2S. DMPT is a source of ubiquitous methyl halides excreted into the global environment. It plays a critical role in osmo-regulation in algae, occuring in large quantities on a global basis. Fresh water marine and esturaine phytoplankton contain DMPT as well. Using algae or fungus can be an inexpensive means of generating methyl iodide, i.e., ponds/lagoons.). REFERENCES:1.W.M.Bayliss and E.H.Starling, Proc.Roy.Soc. 69, 352 (1902)2.Thayer, Olson and Brinckman, Appl.Organometallic Chemistry, 173-9(1987). A novel flow process for metal and oresolubilization by aqueous methyl iodide 3.Thayer and Brinckman, Adv. in Organometallic Chemistry, F.G.A. Stone and West, Eds., Vol. 20, N.Y. Acad. Press, pp 313-56(1982) Challenger and Simpson, JCS, 1591-97(1948)Studies in biological methylation, Part XIII,A-A precursor of the methylsulfide evolved by polysiphonia fastigiata.4.Westwoo, G., Acta Chem.Scand, 20:21131-37 (1966) Denaturation of methylmercury compounds in foodstuffs Craig and Brinckman, Organometallic Compounds in the environment P.J.Craig, Ed., Longman House, London, p.1-61 (1986) 04-8013-06Dimethyl-B-Propiothetin (Dimethylsulfonyl propionate)available in 50 & 100 mg quantities
2-Methoxyestradiol is a drug that prevents the formation of new blood vessels that tumors need in order to grow(angiogenesis). It is derived from estrogen and belongs to the family of drugs called angiogenesis inhibitors (a chemical which signals the process of angiogenesis to stop).Angiogenesisisthe physiological process involving the formation of new blood vessels from pre-existing vessels. This is a normal process in growth and development, as well as in wound healing. However, this is also a fundamental step in the transition of tumors from a dormant state to a malignant state.Cancer cellsare cells that have lost control of their ability to divide in a controlled fashion. A tumor consists of a population of rapidly dividing and growing cancer cells. Mutations rapidly accrue within the population. These mutations (variation) allow the cancer cells (or sub-populations of cancer cells within a tumor) to develop drug resistance and escape therapy. Tumors cannot grow beyond a certain size, generally 1-2 mm3, due to a lack of oxygen and other essential nutrients.Tumorsinduce blood vessel growth (angiogenesis) by secreting various growth factors ( e.g. Vascular Endothelial Growth Factor or VEGF). Growth factors, such as bFGF and VEGF can induce capillary growth into the tumor, supplying required nutrients and allowing for tumor expansion. Thus angiogenesis is a necessary and required step for transition from a small harmless cluster of cells, to a large tumor. Angiogenesis is also required for the spread of a tumor, or metastasis. Single cancer cells can break away from an established solid tumor, enter the blood vessel, and be carried to a distant site, where they can implant and begin the growth of a secondary tumor. Evidence now suggests that the blood vessel in a given solid tumor may be in fact be mosaic vessels, comprised of endothelial cells and tumor cells. This mosaicity allows for substantial shedding of tumor cells into the vasculature. The subsequent growth of such metastases will also require a supply of nutrients and oxygen.Endothelial cells are much more genomically stable than cancer cells, and have a doubling time of approx 120 days. The genomic stability allied to their longevity (compared to the tumor cell), makes then an ideal target for therapies directed against them. They will not 'escape' therapy, as they will not undergo mitosis at such a rapid rate and carry any drug resistance variation through to the next generation within the lifespan of the therapy.Angiogenesisresearch is a cutting edge field in cancer research, and recent evidence also suggests that traditional therapies, such as radiation therapy, may actually work in part by targeting the genomically stable endothelial cell compartment, rather than the genomicaly unstable tumor cell compartment. In short, the therapy is the selection agent which is being used to kill a cell compartment. Tumor cells evolve resistance rapidly due to rapid generation time (days) and genomic instability (variation), whereas endothelial cells are a good target because of a long generation time (months) and genomic stability (low variation).This is a prime example of evolution in action at the cellular level, using a selection pressure to target and differentiate between varying populations of cells. The end result is the extinction of one species or population of cells (endothelial cells), followed by the collapse of the ecosystem (the tumor).Angiogenesis-basedtumour therapy relies on the existence of natural angiogenesis inhibitors like angiostatin, endostatin and tumstatin. These are proteins that mainly originate as specific fragments pre-existing structural proteins like collagen or plasminogen.Product 1895-51,3,5(10)-ESTRATRIEN-2,3,17b-TRIOL 2-METHYLETHER(2-Methoxyestradiol)(Good angiostatic properties) m.w. 302.42 m.p. 183-187o C rot: +111o c=1 methanolavailable in 5 & 25 mg quantities