Amino acids tandem

Cys - Arg, seven-amino acid tandem insertion (residues 121-127) E3 Defective Yes/dominant Warded etal. (1989)... 

CA 27.29 is detected by a monoclonal antibody, B27.29, that is produced against an antigen in ascites of patients with metastatic breast carcinoma. The minimum epitope to which B27.29 reacts is the 8 amino acid sequence (SAPDTRPA) within the 20 amino acid tandem repeating sequence of the mucin core. The reactive sequence of the B27.29 overlaps with the sequence of DF3 used in the CA 15-3 assay. In inhibition studies using labeled MAb, B27.29 effectively competes with DF3 for binding to both CA 27.29 and CA 15-3 antigens. "... 

Burchell, J., Papadimitriou, J. T, Boshell, M., Gendler, S., and Duhig, T, 1989, A short sequence, within the amino acid tandem repeat of a cancer-associated mucin, contains immunodominant epitopes, Int. J. Cancer 44 691-696. 

The ankyrin repeat motif is one of the most common protein-protein interaction domains. Ankyrin repeats are modules of about 33 amino acids repeated in tandem. They are found in a large number of proteins with diverse cellular functions such as transcriptional regulators, signal transducers, cell-cycle regulators, and cytoskeletal proteins. 

Immunreceptor based activation motif. The classical ITAM motif comprises the consensus sequence Yxxl/ Lx(6-12)YxxI/L (where Y stands for tyrosine, I stands for isoleucine, L stands for leucine, and x can be any amino acid). Kinases containing tandem SH2 domains, as for example ZAJP-70 or SYK, recognize the phosphorylated ITAMs, thereby initiating downstream signaling events. 

The Rh2(DOSP)4 catalysts (6b) of Davies have proven to be remarkably effective for highly enantioselective cydopropanation reactions of aryl- and vinyl-diazoacetates [2]. The discovery that enantiocontrol could be enhanced when reactions were performed in pentane [35] added advantages that could be attributed to the solvent-directed orientation of chiral attachments of the ligand carboxylates [59]. In addition to the synthesis of (+)-sertraline (1) [6], the uses of this methodology have been extended to the construction of cyclopropane amino acids (Eq. 3) [35], the synthesis of tricyclic systems such as 22 (Eq. 4) [60], and, as an example of tandem cyclopropanation-Cope rearrangement, an efficient asymmetric synthesis of epi-tremulane 23 (Eq. 5) [61]. 

Chance DH, Adam BW, Smith SJ, Alexander JR, Hillman SL, Hannon WH (1999) Validation of accuracy-based amino acid reference materials in dried-blood spots by tandem mass spectrometry for newborn screening assays. Clin Chem 45 1269-1277. 

Gatlin, C.L., Eng, J.K., Cross, S.T., Detter, J.C., and Yates, J.R III, Automated Identification of amino acid sequence variations in proteins by HPLC/mi-crospray tandem mass spectrometry, Anal. Chem., 72, 757, 2000. 

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

Figure 2.3. A. Mass spectrometer consisting of an ionization source, a mass analyzer and an ion detector. The mass analyzer shown is a time-of -flight (TOF) mass spectrometer. Mass-to-charge (m/z) ratios are determined hy measuring the amount of time it takes an ion to reach the detector. B. Tandem mass spectrometer consisting of an ion source, a first mass analyzer, a collision cell, a second mass analyzer and a detector. The first mass analyzer is used to choose a particular peptide ion to send to the collision cell where the peptide is fragmented. The mass of the spectrum of fragments is determined in the second mass analyzer and is diagnostic of the amino acid sequence of the peptide. Figure adapted from Yates III (2000).

Figure 2.5. Tandem mass spectrometry. A. A peptide mixture is electrosprayed into the mass spectrometer. Individual peptides from the mixture are isolated (circled peptide) and fragmented. B. The fragments from the peptide are mass analyzed to obtain sequence information. The fragments obtained are derived from the N or C terminus of the peptide and are designated "b" or "y" ions, respectively. The spectrum shown indicates peptides that differ in size by the amino acids shown.

Eng, J. K. McCormack, A. L. Yates, J. R. An approach to correlate tandem mass spectra data of peptides with amino acid sequences in a protein database. J. Am. Soc. Mass Spectrom. 1994,5, 976-989. 

Tandem mass spectrometry has become an important tool for determining the sequence of amino acids in protonated peptides98 and the sequence of bases in deprotonated nucleic acids such as DNA.99 Despite the importance and widespread use of CID-MS to sequence peptides and nucleic acids, the mechanistic details of the dissociation processes are poorly understood. A better understanding of the... 

Iida, T., Matsunaga, H., Fukushina, T., Santa, T., Homma, H., Imai, K. (1997). Complete enantiomeric separation of phenylthiocarbamoylated amino acids on a tandem column of reversed and chiral stationary phases. Anal. Chem. 69, 4463-4468. 

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