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Kumar Talluri MVN, Bairwa MK, Theja Dugga HH, Srinivas R. DEVELOPMENT AND VALIDATION OF RP-HPLC AND ULTRAVIOLET SPECTROPHOTOMETRIC METHODS OF ANALYSIS FOR SIMULTANEOUS DETERMINATION OF PARACETAMOL AND LORNOXICAM IN PHARMACEUTICAL DOSAGE FORMS. J LIQ CHROMATOGR R T 2012. [DOI: 10.1080/10826076.2011.597064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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77
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Raju G, Ramesh Babu A, Chandramouli N, Sharma GVM, Srinivas R. Differentiation of Boc-N-protected α/β-hybrid peptides containing β-Caa-L-Ala-β-Caa-OMe and β-Caa-L-Ala-β-Caa-NHMe at the C-terminus by electrospray ionization tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:3369-3374. [PMID: 22006401 DOI: 10.1002/rcm.5223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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78
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Raju B, Ramesh M, Srinivas R, Raju SS, Venkateswarlu Y. Identification and characterization of stressed degradation products of prulifloxacin using LC–ESI-MS/Q-TOF, MSn experiments: Development of a validated specific stability-indicating LC–MS method. J Pharm Biomed Anal 2011; 56:560-8. [DOI: 10.1016/j.jpba.2011.06.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 06/22/2011] [Accepted: 06/25/2011] [Indexed: 11/28/2022]
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79
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Yadav JS, Reddy BVS, Venugopal C, Srinivas R, Ramalingam T. MICROWAVE-ACCELERATED SYNTHESIS OF 4-CHLOROTETRAHYDROPYRANS BY BISMUTH(III) CHLORIDE*. SYNTHETIC COMMUN 2011. [DOI: 10.1081/scc-120004059] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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80
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Borkar RM, Raju B, Srinivas R, Patel P, Shetty SK. Identification and characterization of stressed degradation products of metoprolol using LC/Q-TOF-ESI-MS/MS and MS(n) experiments. Biomed Chromatogr 2011; 26:720-36. [PMID: 21989963 DOI: 10.1002/bmc.1721] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 09/05/2011] [Indexed: 11/06/2022]
Abstract
A rapid, specific and reliable isocratic high-performance liquid chromatography combined with quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS) method has been developed and validated for the identification and characterization of stressed degradation products of metoprolol. Metoprolol, an anti-hypertensive drug, was subjected to hydrolysis (acidic, alkaline and neutral), oxidation, photolysis and thermal stress, as per ICH-specified conditions. The drug showed extensive degradation under oxidative and hydrolysis (acid and base) stress conditions. However, it was stable to thermal, neutral and photolysis stress conditions. A total of 14 degradation products were observed and the chromatographic separation of the drug and its degradation products was achieved on a C(18) column (4.6 × 250 mm, 5 µm). To characterize degradation products, initially the mass spectral fragmentation pathway of the drug was established with the help of MS/MS, MS(n) and accurate mass measurements. Similarly, fragmentation pattern and accurate masses of the degradation products were established by subjecting them to LC-MS/QTOF analysis. Structure elucidation of degradation products was achieved by comparing their fragmentation pattern with that of the drug. The degradation products DP(2) (m/z 153) and DP(14) (m/z 236) were matched with impurity B, listed in European Pharmacopoeia and British Pharmacopoeia, and impurity I, respectively. The LC-MS method was validated with respect to specificity, linearity, accuracy and precision.
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George M, Ramesh V, Srinivas R, Giblin D, Gross ML. Deprotonated N-(2,4-Dinitrophenyl)amino Acids Undergo Cyclization in Solution and the Gas Phase. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2011; 306:232-240. [PMID: 21966244 PMCID: PMC3181136 DOI: 10.1016/j.ijms.2011.01.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The collisionally activated mass spectral fragmentations of N-(2,4-dinitrophenyl)alanine and phenylalanine [M - H](-) may be gas-phase analogs of the base-catalyzed cyclization of N-(2,4-dinitrophenyl)amino acids in aqueous dioxane. This latter reaction is one source of the 2-substituted 5-nitro-1H-benzimidazole-3-oxides, which are antibacterial agents. The fragmentation of both compounds, established by tandem mass spectrometric experiments and supported by molecular modeling using DFT methods, indicate that the [M - H](-) ions dissociate via sequential eliminations of CO(2) and H(2)O to produce deprotonated benzimidazole-N-oxide derivatives. The gas-phase cyclization reactions are analogous to the base-catalyzed cyclization in solution, except that in the latter case, the reactant must be a dianion for the reaction to occur on a reasonable time scale. The cyclization of N-(2-nitrophenyl)phenylalanine, which has one less nitro group, requires a stronger base for the cyclization than the compound with a second nitro group at the 4-position. Following losses of CO(2) and H(2)O are expulsions of both neutral molecules and free radicals, the latter being examples of violations of the even-electron ion rule.
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Ramesh M, Raju B, Srinivas R, Sureshbabu VV, Vishwanatha TM, Hemantha HP. Characterization of Nα-Fmoc-protected dipeptide isomers by electrospray ionization tandem mass spectrometry (ESI-MS(n)): effect of protecting group on fragmentation of dipeptides. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:1949-1958. [PMID: 21698678 DOI: 10.1002/rcm.5076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A series of positional isomeric pairs of Fmoc-protected dipeptides, Fmoc-Gly-Xxx-OY/Fmoc-Xxx-Gly-OY (Xxx=Ala, Val, Leu, Phe) and Fmoc-Ala-Xxx-OY/Fmoc-Xxx-Ala-OY (Xxx=Leu, Phe) (Fmoc=[(9-fluorenylmethyl)oxy]carbonyl) and Y=CH(3)/H), have been characterized and differentiated by both positive and negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-IT-MS(n)). In contrast to the behavior of reported unprotected dipeptide isomers which mainly produce y(1)(+) and/or a(1)(+) ions, the protonated Fmoc-Xxx-Gly-OY, Fmoc-Ala-Xxx-OY and Fmoc-Xxx-Ala-OY yield significant b(1)(+) ions. These ions are formed, presumably with stable protonated aziridinone structures. However, the peptides with Gly- at the N-terminus do not form b(1)(+) ions. The [M+H](+) ions of all the peptides undergo a McLafferty-type rearrangement followed by loss of CO(2) to form [M+H-Fmoc+H](+). The MS(3) collision-induced dissociation (CID) of these ions helps distinguish the pairs of isomeric dipeptides studied in this work. Further, negative ion MS(3) CID has also been found to be useful for differentiating these isomeric peptide acids. The MS(3) of [M-H-Fmoc+H](-) of isomeric peptide acids produce c(1)(-), z(1)(-) and y(1)(-) ions. Thus the present study of Fmoc-protected peptides provides additional information on mass spectral characterization of the dipeptides and distinguishes the positional isomers.
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Gunjal RP, Raju G, Babu AR, Mallikarjun N, Shastri N, Srinivas R. HPLC AND LC-MS STUDIES ON STRESS DEGRADATION BEHAVIOR OF LEVOCETIRIZINE AND DEVELOPMENT OF A VALIDATED SPECIFIC STABILITY-INDICATING METHOD. J LIQ CHROMATOGR R T 2011. [DOI: 10.1080/10826076.2011.564704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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84
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Karandikar AA, Pushparajan S, Unni MN, Srinivas R. Case Report: Cerebrotendinous xanthomatosis. Indian J Radiol Imaging 2011; 19:314-7. [PMID: 19881113 PMCID: PMC2797749 DOI: 10.4103/0971-3026.57218] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cerebrotendinous xanthomatosis is a rare genetic disorder. We present and discuss the clinical, radiological, and histopathologic findings in a 36-year-old woman who had juvenile cataract, childhood diarrhea, mental retardation, cerebellar ataxia, and bilateral Achilles tendon xanthomas. She was thoroughly investigated radiologically and biopsy confirmed the diagnosis of xanthomas.
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85
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Raju B, Ramesh M, Srinivas R, Chandrasekhar S, Kiranmai N, Sarma VUM. Differentiation of positional isomers of hybrid peptides containing repeats of β-nucleoside derived amino acid (β-Nda-) and L-amino acids by positive and negative ion electrospray ionization tandem mass spectrometry (ESI-MSn). JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:703-717. [PMID: 21472609 DOI: 10.1007/s13361-010-0070-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 11/19/2010] [Accepted: 12/26/2010] [Indexed: 05/30/2023]
Abstract
A new class of positional isomeric pairs of -Boc protected oligopeptides comprised of alternating nucleoside derived β-amino acid (β-Nda-) and L-amino acid residues (alanine, valine, and phenylalanine) have been differentiated by both positive and negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-MS(n)). The protonated dipeptide positional isomers with β-Nda- at the N-terminus lose CH(3)OH, NH(3), and C(2)H(4)O(2), whereas these processes are absent for the peptides with L-amino acids at the N-terminus. Instead, the presence of L-amino acids at the N-terminus results in characteristic retro-Mannich reaction involving elimination of imine. A good correlation has been observed between the conformational structure of the peptides and the abundance of y(n)(+) and b(n)(+) ions in MS(n) spectra. In the case of tetrapeptide isomers that are reported to form helical structures in solution phase, no y(n)(+) and b(n)(+) ions are observed when the corresponding amide -NH- participates in the helical structures. In contrast, significant y(n)(+) and b(n)(+) ions are formed when the amide -NH- is not involved in the H-bonding. In the case of tetra- and hexapeptides, it is observed that abundant b(n)(+) ions are formed, presumably with stable oxazolone structures when the C-terminus of the b(n)(+) ions possessed L-amino acid and the β-Nda- at the C-terminus appears to prevent the cyclization process leading to the absence of corresponding b(n)(+) ions.
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Rao RN, Maurya PK, Ramesh M, Srinivas R, Agwane SB. Development of a validated high-throughput LC-ESI-MS method for determination of sirolimus on dried blood spots. Biomed Chromatogr 2011; 24:1356-64. [PMID: 21077255 DOI: 10.1002/bmc.1450] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A high-throughput liquid chromatography-electrospray ionization mass spectrometric (LC-ESI-MS) method for screening of sirolimus on dried blood spots (DBS) was developed and validated. It involves solvent extraction of a punch of DBS followed by reversed-phase LC on a relatively new monolithic column consisting of a silica rod with bimodal pore structure and detection by ESI-MS. The run time was less than 3 min with a very low backpressure at a flow rate of 0.5 mL/min. The method can analyze more than 100 samples in an 8 h working day, including sample preparation. The assay was linear from 1 to 100 ng/mL. The mean recovery was 92.42%. The mean inter-day and intra-day precisions were 1.23 and 1.41%, respectively. The developed method is simple, rapid and useful for clinical applications.
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87
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Ramesh M, Raju B, Srinivas R, Sureshbabu VV, Narendra N, Vasantha B. Characterization of Nα-Fmoc-protected ureidopeptides by electrospray ionization tandem mass spectrometry (ESI-MS/MS): differentiation of positional isomers. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:1461-1472. [PMID: 21053379 DOI: 10.1002/jms.1862] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Four pairs of positional isomers of ureidopeptides, FmocNH-CH(R(1))-ϕ(NH-CO-NH)-CH(R(2))-OY and FmocNH-CH(R(2))-ϕ(NH-CO-NH)-CH(R(1))-OY (Fmoc = [(9-fluorenyl methyl)oxy]carbonyl; R(1) = H, alkyl; R(2) = alkyl, H and Y = CH(3)/H), have been characterized and differentiated by both positive and negative ion electrospray ionization (ESI) ion-trap tandem mass spectrometry (MS/MS). The major fragmentation noticed in MS/MS of all these compounds is due to --N--CH(R)--N--bond cleavage to form the characteristic N- and C-terminus fragment ions. The protonated ureidopeptide acids derived from glycine at the N-terminus form protonated (9H-fluoren-9-yl)methyl carbamate ion at m/z 240 which is absent for the corresponding esters. Another interesting fragmentation noticed in ureidopeptides derived from glycine at the N-terminus is an unusual loss of 61 units from an intermediate fragment ion FmocNH = CH(2) (+) (m/z 252). A mechanism involving an ion-neutral complex and a direct loss of NH(3) and CO(2) is proposed for this process. Whereas ureidopeptides derived from alanine, leucine and phenylalanine at the N-terminus eliminate CO(2) followed by corresponding imine to form (9H-fluoren-9-yl)methyl cation (C(14)H(11) (+)) from FmocNH = CHR(+). In addition, characteristic immonium ions are also observed. The deprotonated ureidopeptide acids dissociate differently from the protonated ureidopeptides. The [M - H](-) ions of ureidopeptide acids undergo a McLafferty-type rearrangement followed by the loss of CO(2) to form an abundant [M - H - Fmoc + H](-) which is absent for protonated ureidopeptides. Thus, the present study provides information on mass spectral characterization of ureidopeptides and distinguishes the positional isomers.
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88
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Sabitha G, Bhikshapathi M, Nayak S, Srinivas R, Yadav JS. Triton B catalyzed three-component, one-pot synthesis of 2-amino-2-chromenes at ambient temperature. J Heterocycl Chem 2010. [DOI: 10.1002/jhet.544] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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89
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Charkravarti A, Wang M, Robins I, Guha A, Curren W, Brachman D, Schultz C, Choucair A, Dolled-Filhart M, Christiansen J, Gustavson M, Molinaro A, Mischel P, Lautenschlaeger T, Dicker A, Mehta M, Phillips CA, Dhulibala S, Hallahan D, Jaboin J, Cardinale FS, Dickey P, Goodrich I, Gorelick J, Sinha R, Dest VM, Chen C, Olsen C, Franklin W, Kleinschmidt-DeMasters B, Kavanagh BD, Lillehei K, Waziri A, Damek D, Gaspar LE, Stauder MC, Laack NN, Link MJ, Pollock BE, Schomberg PJ, Fraser JF, Pannullo SC, Moliterno J, Cobb W, Stieg PE, Vinchon-Petit S, Jarnet D, Michalak S, Lewis A, Benoit JP, Menei P, Desmarais G, Paquette B, Bujold R, Mathieu D, Fortin D, Cuneo KC, Vredenburgh JJ, Sampson JH, Reardon DA, Desjardins A, Peters KL, Kirkpatrick JP, Patel PN, Vyas R, Suryanarayan U, Bhavsar D, Mehta M, Hayhurst C, Monsalves E, Van Prooijen M, Menard C, Zadeh G, Chung C, Burrell K, Lindsey P, Menard C, Zadeh G, Burri SH, Asher AL, Kelly RB, Boltes P, Fraser RW, Dilmanian FA, Rusek A, Desnoyers NR, Park JY, Dane B, Dioszegi I, Hurley SD, O'Banion MK, Tomasi D, Wang R, Meek AG, Sleire L, Wang J, Heggdal J, Pedersen PH, Enger PO, Clump DA, Srinivas R, Wegner RE, Heron DE, Burton SA, Mintz AH, Howard SP, Robins HI, Tome WA, Paravati AJ, Heron DE, Gardner PA, Snyderman C, Ozhasoglu C, Quinn A, Burton SA, Seelman K, Seelman K, Mintz AH, Chang JH, Park YG, Mehta MJ, Patel PN, Vyas RK, Bhavsar DC, Guarnaschelli JN, Imwalle L, Ying J, McPherson C, Warnick R, Breneman J, Khwaja SS, Laack NN, Wetjen NM, Brown PD, Siedow M, Nestler U, Perry J, Huebner A, Chakravarti A, Lautenschlaeger T, Glass J, Andrews D, Werner-Wasik M, Evans J, Lawrence R, Martinez N, Anuradha G, David M, Sara M, Mark L, Ricardo B, Jeff J, Juan H, Kozono D, Zinn P, Ng K, Chen C, Melian E, Prabhu V, Sethi A, Barton K, Anderson D, Rockne RC, Mrugala M, Rockhill J, Swanson KR. Radiation Therapy. Neuro Oncol 2010. [DOI: 10.1093/neuonc/noq116.s15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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90
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Ramesh Babu A, Sridhar Y, Raju G, Swamy NS, Srihari P, Ramesh V, Srinivas R. Diastereomeric differentiation of two pairs of glycal derivatives by electrospray ionization tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:2776-2780. [PMID: 20814985 DOI: 10.1002/rcm.4691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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91
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Raju G, Ramesh V, Srinivas R, Sharma GVM, Shoban Babu B. Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:651-663. [PMID: 20527034 DOI: 10.1002/jms.1756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Two new series of Boc-N-alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptides containing repeats of L-Ala-delta(5)-Caa/delta(5)-Caa-L-Ala and beta(3)-Caa-delta(5)-Caa/delta(5)-Caa-beta(3)-Caa (L-Ala = L-alanine, Caa = C-linked carbo amino acid derived from D-xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MS(n) spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc-group, and the side chain. The dipeptide positional isomers are differentiated by the collision-induced dissociation (CID) of the protonated peptides. The loss of 2-methylprop-1-ene is more pronounced for Boc-NH-L-Ala-delta-Caa-OCH(3) (1), whereas it is totally absent for its positional isomer Boc-NH-delta-Caa-L-Ala-OCH(3) (7), instead it shows significant loss of t-butanol. On the other hand, second isomeric pair shows significant loss of t-butanol and loss of acetone for Boc-NH-delta-Caa-beta-Caa-OCH(3) (18), whereas these are insignificant for its positional isomer Boc-NH-beta-Caa-delta-Caa-OCH(3) (13). The tetra- and hexapeptide positional isomers also show significant differences in MS(2) and MS(3) CID spectra. It is observed that 'b' ions are abundant when oxazolone structures are formed through five-membered cyclic transition state and cyclization process for larger 'b' ions led to its insignificant abundance. However, b(1)(+) ion is formed in case of delta,alpha-dipeptide that may have a six-membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di-, tetra-, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers.
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92
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Kulkarni HM, Ramesh V, Srinivas R, Jagannadham M. Acetylating Tryptic Peptides Enhances b Ion Intensity in MALDI TOF/TOF: Implications in Peptide Sequencing and Identification of Proteins in an Antarctic Bacterium Pseudomonas Syringae. PROTEOMICS INSIGHTS 2010. [DOI: 10.4137/pri.s3676] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Several approaches have been described to identify proteins from MALDI MS/MS mass spectra. The sequence of tryptic peptides is determined by database searching or by de novo sequencing. Different algorithms are available to determine peptide sequence using mass spectra. False discovery of peptides is an associated problem with it. A combination of chemical modifications followed by mass spectral analysis helps in overcoming this problem. Acetylating the tryptic peptides of β-galactosidase in methanol is found to increase the b-ion signal intensity in MALDI TOF mass spectrometry. The method of acetylation is extended to the tryptic peptides of the proteins of an Antarctic bacterium Pseudomonas syringae, whose genome sequence is not known. These proteins are identified by searching the available database of the Pseudomonas spp at NCBI using the MS/MS spectra. The sequences of the peptides are validated using the CID mass spectra of the acetylated tryptic peptides.
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93
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Karandikar AA, Pushparajan S, Unni MN, Srinivas R. Case Report: Cerebrotendinous xanthomatosis. Indian J Radiol Imaging 2009. [PMID: 19881113 DOI: 10.4103/0971‐3026.57218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Cerebrotendinous xanthomatosis is a rare genetic disorder. We present and discuss the clinical, radiological, and histopathologic findings in a 36-year-old woman who had juvenile cataract, childhood diarrhea, mental retardation, cerebellar ataxia, and bilateral Achilles tendon xanthomas. She was thoroughly investigated radiologically and biopsy confirmed the diagnosis of xanthomas.
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94
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Raju B, Ramesh V, Sudhakar A, Ramesh M, Sarma VUM, Chandrasekhar S, Srinivas R. Diastereomeric differentiation of norbornene amino acid peptides by electrospray ionization tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:2965-2974. [PMID: 19681066 DOI: 10.1002/rcm.4211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A new class of diastereomeric pairs of non-natural amino acid peptides derived from butyloxycarbonyl (Boc-)protected cis-(2S,3R)- and trans-(2S,3S)-beta-norbornene amino acids including a monomeric pair have been investigated by electrospray ionization (ESI) tandem mass spectrometry using quadrupole time-of-flight (Q-TOF) and ion-trap mass spectrometers. The protonated cis-BocN-beta-nbaa (2S,3R) (1) (betanbaa = beta-norbornene amino acid) eliminates the Boc group to form [M+H-Boc+H](+), whereas an additional ion [M+H-C(4)H(8)](+) is formed from trans-BocN-beta-nbaa (2S,3S) (2). Similarly, it is observed that the peptide diastereomers (di-, tri- and tetra-), with cis-BocN-beta-nbaa (2S,3R)- at the N-terminus, initially eliminate the Boc group to form [M+H-Boc+H](+) which undergo further fragmentation to give a set of product ions that are different for the peptides with trans-BocN-beta-nbaa (2S,3S)- at the N-terminus. Thus the Boc group fragments differently depending on the configuration of the amino acid present at the N-terminus. It is also observed that the peptide bond cleavage in these peptides is less favoured and most of the product ions are formed due to retro-Diels-Alder fragmentation. Interestingly, sodium-cationized peptide diastereomers mainly yield a series of retro-Diels-Alder fragment ions which are different for each diastereomer as they are formed starting from [M+Na-Boc+H](+) in peptides with cis-BocN-beta-nbaa (2S,3R)- at the N-terminus, and [M+Na-C(4)H(8)](+) in peptides with trans-BocN-beta-nbaa (2S,3S)- at the N-terminus. All these results clearly indicate that these diastereomeric pairs of peptides yield characteristic product ions which help distinguish the isomers.
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95
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Ramesh M, Ramesh V, Raju B, Srinivas R, Kumaraswamy G, Markondaiah B, Padmaja M. Diastereomeric differentiation of Oppolzer sultam derivatives using electrospray ionization and atmospheric pressure photo ionization tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2009; 44:1114-1118. [PMID: 19229890 DOI: 10.1002/jms.1567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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96
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97
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Ramesh V, Srinivas R, Kumaraswamy G, Markondaiah B. Diastereoselectivity in the McLafferty-type rearrangement of protonated precursors of belactosin derivatives using electrospray ionization (ESI) and atmospheric pressure photo ionization (APPI) tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2009; 44:285-287. [PMID: 18853474 DOI: 10.1002/jms.1499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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98
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Ramesh V, Ramesh M, Srinivas R, Sharma GVM, Jayaprakash P. Electrospray ionization tandem mass spectrometric study on the effect of N-terminal beta- and gamma-carbo amino acids on fragmentation of GABA-hybrid peptides. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:3339-3352. [PMID: 18837002 DOI: 10.1002/rcm.3743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The fragmentations of protonated and deprotonated ions of a new class of N-blocked hybrid Boc-carbopeptides containing repeats of gamma-Caa/gammaAbu- and beta-Caa/gammaAbu- (Caa==C-linked carbo gamma(4)-/beta(3)- amino acids derived from D-xylose, gammaAbu = gamma-aminobutyric acid) have been studied using electrospray ionization (ESI) ion-trap tandem mass spectrometry (MS/MS). MS/MS of a pair of these protonated diastereomers produces distinct fragmentation of the Boc group. The formation of [M + H-56](+) corresponding to loss of isobutylene is more pronounced for Boc-NH-(R)-gamma-Caa-gammaAbu-OH (2) whereas it is of low abundance for Boc-NH-(S)-gamma-Caa-gammaAbu--OH (1). Similarly, MS(2) of [M--H](-) of 2 produces an abundant [M--H--C(CH(3))(3)OH--CO(2)](-) ion, which is absent for its diastereomeric isomer 1. From this, it can be suggested that MS/MS of N-blocked Boc-protected carbopeptides may be helpful in distinguishing the stereochemistry of the N-terminus Caa. MS(3) of [M + H-Boc + H](+) ions of peptides with a gamma-amino acid (gamma-Caa/gammaAbu) at the N-terminus produces only abundant y(n) (+) ions. On the other hand, characteristic fragmentations involving the peptide backbone (b(n) (+) and y(n) (+)) and the side chain are seen when beta-Caa is at the N-terminus of the peptides. MS(3) of the [M--H--C(CH(3))(3)OH](-) ion of peptides containing gamma-Caa/gammaAbu at the N-terminus gave y(n) (-) and [M--H--C(CH(3))(3)OH--CO(2)](-) ions, whereas the presence of beta-Caa at the N-terminus yielded predominantly [M--H--C(CH(3))(3)OH--HNCO](-). Thus, on the basis of our previous study and that presented here we propose that the fragmentation of these hybrid carbopeptides is highly influenced by the type of carbo amino acid present at the N-terminus.
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Ghanta SR, Srinivas R, Rhodes CT. Use of Mixer-Torque Measurements as an Aid to Optimizing Wet Granulation Process. Drug Dev Ind Pharm 2008. [DOI: 10.3109/03639048409064652] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Ramesh V, Srinivas R, Sharma GVM, Jayaprakash P, Kunwar AC. Differentiation of three pairs of Boc-beta,gamma- and gamma,beta-hybrid peptides by electrospray ionization tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2008; 43:1201-1214. [PMID: 18320536 DOI: 10.1002/jms.1393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A new series of Boc-N-beta(3), gamma(4)-/gamma(4), beta(3)-isomeric hybrid peptides (containing repeats of beta(3)-Caa and gamma(4)-Caa's, Caa = C-linked carbo beta(3)-/gamma(4)-amino acids derived from D-xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion-trap and high resolution quadrupole time-of-flight/tandem mass spectrometry (Q-TOF MS/MS). MS(n) of protonated isomeric peptides and [M+H-Boc+H](+) produce characteristic fragmentation involving the peptide backbone, the Boc-group, and the side chain. The positional isomers are differentiated from one another by the presence of y(n)(+), b(n)(+), and other fragment ions of different m/z values. It is observed that the peptides with beta-Caa at the N-terminus produce extensive fragmentation, whereas gamma-Caa gave rise to much less fragmentation. Peptides with gamma-Caa at the N-terminus lose NH(3), whereas this process is absent for the carbopeptides with beta-Caa at the N-terminus. Two pairs of dipeptide diastereomers are clearly differentiated by the collision-induced dissociation (CID) of their protonated molecules. The loss of 2-methylprop-1-ene is more pronounced for Boc-NH-(R)-beta-Caa-(R)-gamma-Caa-OCH(3) (6) and Boc-NH-(R)-gamma-Caa-(R)-beta-Caa-OCH(3) (12), whereas it is insignificant or totally absent for its protonated diastereomeric pair Boc-NH-(S)-beta-Caa-(S)-gamma-Caa-OCH(3) (1) and Boc-NH-(S)-gamma-Caa-(S)-beta-Caa-OCH(3) (7). Further, ESI negative ion tandem mass spectrometry has also been found to be useful for differentiating these isomeric peptide acids.
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