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Martin RB, Parcell A. Hydrolysis of 2-Methyl-Δ2 -oxazoline. An Intramolecular O-N-Acetyl Transfer Reaction. J Am Chem Soc 2002. [DOI: 10.1021/ja01484a033] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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77
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Tribolet R, Martin RB, Sigel H. Ternary complexes in solution. Part 49. Intramolecular equilibria in metal ion complexes of adenosine 5'-triphosphate (ATP4-): coordination of ammonia or imidazole to M(ATP)2- releases N-7 from the metal ion coordination sphere. Inorg Chem 2002. [DOI: 10.1021/ic00252a003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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78
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Martin RB, Niemann C. THE CALCIUM CHLORIDE AND HYDROXYL ION CATALYZED HYDROLYSIS OF SEVERAL ACYLATED α-AMINO ACID ESTERS. J Am Chem Soc 2002. [DOI: 10.1021/ja01578a068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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79
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Martin RB, Niemann C. THE EFFECT OF SODIUM CHLORIDE ON THE alpha-CHYMOTRYPSIN CATALYZED HYDROLYSIS OF METHYL HIPPURATE. J Am Chem Soc 2002. [DOI: 10.1021/ja01574a065] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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80
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Donato H, Martin RB. Dipolar shifts and structure in aqueous solutions of 3:1 lanthanide complexes of 2,6-dipicolinate. J Am Chem Soc 2002. [DOI: 10.1021/ja00767a011] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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81
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Sinn E, Flynn CM, Martin RB. Crystal and molecular structure of dichlorobis(1-methylcytosine)palladium(II). Inorg Chem 2002. [DOI: 10.1021/ic50175a048] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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82
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Martin RB. Enzyme and Metabolic Inhibitors. Vol. 1. General Principles of Inhibition. J Med Chem 2002. [DOI: 10.1021/jm00342a058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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83
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Martin RB, Hedrick RI, Parcell A. Thiazoline and Oxazoline Hydrolyses and Sulfur-Nitrogen and Oxygen-Nitrogen Acyl Transfer Reactions. J Org Chem 2002. [DOI: 10.1021/jo01034a018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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84
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Martin RB. Invariance of disulfide stretching wave numbers to disulfide dihedral angles. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100601a022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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85
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Espersen WG, Hutton WC, Chow ST, Martin RB. Cautions concerning uses of copper(II) selective broadening in nuclear magnetic resonance spectroscopy for determination of ligand binding sites. J Am Chem Soc 2002. [DOI: 10.1021/ja00833a045] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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88
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Yeagle PL, Hutton WC, Martin RB. Nuclear Overhauser effect in phosphorus-31 nuclear magnetic resonance. J Am Chem Soc 2002. [DOI: 10.1021/ja00857a043] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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89
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Scheller KH, Scheller-Krattiger V, Martin RB. Equilibriums in solutions of nucleosides, 5'-nucleotides, and diethylenetriaminepalladium(2+). J Am Chem Soc 2002. [DOI: 10.1021/ja00413a009] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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90
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91
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Van Wart HE, Scheraga HA, Martin RB. Agreement concerning the nature of the variation of disulfide stretching frequencies with disulfide dihedral angles. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100557a017] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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92
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Applewhite TH, Martin RB, Niemann C. The α-Chymotrypsin-catalyzed Hydrolysis of Methyl Hippurate in Aqueous Solutions at 25° and pH 7.9, its Inhibition by Indole and its Dependence upon Added Non-aqueous Solvents1. J Am Chem Soc 2002. [DOI: 10.1021/ja01539a046] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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93
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Martin RB, Lowey S, Elson EL, Edsall JT. Hydrolysis of 2-Methyl-Δ2-thiazoline and its Formation from N-Acetyl-β-mercaptoethylamine. Observations on an N-S Acyl Shift1. J Am Chem Soc 2002. [DOI: 10.1021/ja01528a018] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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94
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Martin RB, Edsall JT. The Association of Divalent Cations with Acylated Histidine Derivatives1. J Am Chem Soc 2002. [DOI: 10.1021/ja01490a023] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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95
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Martin RB. Size, structure and gender: lessons about fracture risk. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2002; 2:209-11. [PMID: 15758435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The differences in age-related fracture risks among men and women must reflect gender differences in the relevant variables. We are concerned here with gender differences in structural variables that relate to the size and shape of bones. As children grow, their bones grow in diameter through periosteal modeling. Studies show that radial growth is driven by mechanical forces and is not just "genetically programmed". Moving bone mass farther from the center of the diaphysis makes it more effective in resisting bending and twisting forces, and disproportionately so in comparison to changes in bone mass. Gender differences in long bone structure appear to arise because the bone cells of males and females function in different hormonal environments which affect their responses to mechanical loading. In girls, bone formation on the metacarpal periosteal surface essentially stops at puberty, and is replaced by formation on the endosteal surface, reducing endosteal diameter until about age 20. Bone strength is 60% greater in male metacarpals than in those of females because bone is added periosteally in boys and endosteally in girls. At menopause endosteal resorption resumes, accompanied by slow periosteal apposition, weakening cortical structure. Similar phenomena occur in such critical regions as the femoral neck. Another fundamental gender difference in skeletal development is that whole body bone mineral content increases in linear proportion to lean body mass throughout skeletal maturation in boys, but in girls there is a distinct increase in the slope of this relationship at puberty, when estrogen rises. Frost's hypothesis is that this reflects an effect of estrogen on bone's mechanostat set point, and this is increasingly supported by data showing that estrogen and mechanical strain act through a common pathway in osteoblast-like cells. If Frost's hypothesis is correct, the mechanostat is set for maximal effect of mechanical loading on bone gain during the 2-3 years preceding menarche. During the childbearing years, the set point is at an intermediate level, and at menopause, it shifts again to place the skeleton into the metabolic equivalent of a disuse state. The most direct approach to resolving this problem would be to simulate the putative effect of estrogen on the set point itself.
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Tarantal AF, Castillo A, Ekert JE, Bischofberger N, Martin RB. Fetal and maternal outcome after administration of tenofovir to gravid rhesus monkeys (Macaca mulatta). J Acquir Immune Defic Syndr 2002; 29:207-20. [PMID: 11873070 DOI: 10.1097/00042560-200203010-00001] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Tenofovir has been shown to cross the placenta in quantities sufficient to sustain reductions in viral load in simian immunodeficiency virus (SIV)-infected fetal monkeys. With chronic exposure (30 mg/kg), however, significant bone-related toxicity has been shown in approximately 25% of infants studied. Further investigations were conducted to determine whether the bone-related toxicity observed was initiated during fetal life. Gravid rhesus monkeys (n = 4) were administered tenofovir subcutaneously once daily from 20 to 150 days of gestation (30 mg/kg; term: 165 +/- 10 days). Fetuses were monitored sonographically, and maternal and fetal blood and urine samples were collected to assess hematologic parameters, clinical chemistry, insulin-like growth factor (IGF) levels, and bone biomarkers. Fetuses were delivered by hysterotomy near term for necropsy and evaluation of bone-related mechanical properties. Results of these studies have shown 1) normal fetal development, although overall body weights and crown-rump lengths were less than those for age-matched controls (p < or = .03); 2) a significant reduction in circulating IGF-I (p <.001); 3) a small reduction in fetal bone porosity (p < or = .03); and 4) transient alterations in maternal body weights and bone-related biomarkers during the treatment period. The results of these studies suggest that chronic fetal exposure to tenofovir at the maternal dose of 30 mg/kg throughout gestation can alter select fetal parameters and transiently affect maternal bone biomarkers.
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Abstract
There is increasing interest in the degree to which bone remodeling, particularly in cortical bone, is "targeted" at fatigue microdamage. The theory that microdamage initiates remodeling in close proximity to microcracks, thereby removing them, and that this accounts for a significant fraction of the overall remodeling activity, has been gaining acceptance. However, the association between the initial, resorptive stage of remodeling and microcracks in histologic sections of cortical bone is far from complete; indeed, the great majority of resorption spaces are not spatially associated with microcracks. This observation has maintained support for the older concept that most remodeling occurs primarily for such metabolic purposes as calcium homeostasis. To gain further insight regarding the degree to which microdamage governs remodeling, this study presents a mathematical analysis based on the unorthodox hypothesis that all cortical bone remodeling is initiated by, and in close proximity to, microcracks. Equations are derived showing that, because remodeling basic multicellular units (BMUs) travel several millimeters beyond their point of initiation, the relative numbers of resorption spaces and microcracks found in close spatial proximity or isolated from one another are consistent with the hypothesis. The results also predict the degree to which the spatial association between resorption spaces and microcracks should exceed that due to chance alone. There are as yet very limited experimental data suitable for testing this model, but the existing data closely correspond to the model's predictions.
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98
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Hutchinson TM, Bakulin AV, Rakhmanov AS, Martin RB, Steele CR, Arnaud SB. Effects of chair restraint on the strength of the tibia in rhesus monkeys. J Med Primatol 2001; 30:313-21. [PMID: 11990531 DOI: 10.1034/j.1600-0684.2001.300605.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To determine the effects of the relative inactivity and unloading on the strength of the tibias of monkeys, Macaca mulatta, we used a non-invasive test to measure bending stiffness, or EI (Nm2), a mechanical property. The technique was validated by comparisons of in vivo measurements with standard measures of EI in the same bones post-mortem (r2 = 0.95, P < 0.0001). Inter-test precision was 4.28+/-1.4%. Normative data in 24 monkeys, 3.0+/-0.7 years and 3.6+/-0.6 kg, revealed EI to be 16% higher in the right than left tibia (4.4+/-1.6 vs. 3.7+/-1.6 Nm2, P < 0.05). Five monkeys, restrained in chairs for 14 days, showed decreases in EI. There were no changes in EI in two chaired monkeys that lost weight during a 2-week space flight. The factors that account for both the decreases in bone mechanical properties after chair restraint at 1 g and lack of change after microgravity remain to be identified. Metabolic factors associated with body weight changes are suggested by our results.
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Sigel H, Bianchi EM, Corfù NA, Kinjo Y, Tribolet R, Martin RB. Stabilities and isomeric equilibria in solutions of monomeric metal-ion complexes of guanosine 5'-triphosphate (GTP4-) and inosine 5'-triphosphate (ITP4-) in comparison with those of adenosine 5'-triphosphate (ATP4-). Chemistry 2001; 7:3729-37. [PMID: 11575773 DOI: 10.1002/1521-3765(20010903)7:17<3729::aid-chem3729>3.0.co;2-e] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Under experimental conditions in which the self-association of the purine-nucleoside 5'-triphosphates (PuNTPs) GTP and ITP is negligible, potentiometric pH titrations were carried out to determine the stabilities of the M(H;PuNTP) and M(PuNTP)2-complexes where M2+ = Mg2+, Ca2+, Sr2+. Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+ (I = 0.1 M, 25 degrees C). The stabilities of all M(GTP)2- and M(ITP)2- complexes are significantly larger than those of the corresponding complexes formed with pyrimidine-nucleoside 5'-triphosphates (PyNTPs), which had been determined previously under the same conditions. This increased complex stability is attributed, in agreement with previous 1H MNR shift studies, to the formation of macrochelates of the phosphate-coordinated metal ions with N7 of the purine residues. A similar enhanced stability (despite relatively large error limits) was observed for the M(H;PuNTP) complexes, in which H+ is bound to the terminal y-phosphate group, relative to the stability of the M(H;PyNTP)- species. The percentage of the macrochelated isomers in the M(GTP)2- and M(ITP)2- systems was quantified by employing the difference log KMM(PuNTP)-log KMM(PyNTP); the lowest and highest formation degrees of the macrochelates were observed for Mg(ITP)2- and Cu(GTP)2- with 17 +/- 11% and 97 +/- 1%, respectively. From previous studies of M(ATP)2- complexes, it is known that innersphere and outersphere macrochelates may form; that is, in the latter case a water molecule is between N7 and the phosphate-coordinated M2+. Similar conclusions are reached now by comparisons with earlier 1H MNR shift measurements, that is, that Mg(GTP)2- (21 +/- 11%), for example, exists largely in the form of an outersphere macrochelate and Zn(GTP)2- (68 +/- 4%) as an innersphere one. Generally, the overall percentage of macrochelate falls off for a given metal ion in the order M(GTP)2- > M(ITP)2- > M(ATP)2-; this is in accord with the decreasing basicity of N7 and the steric inhibition of the (C6)NH2 group in the adenine residue. Furthermore, although the absolute stability constants of the previously studied M(GMP), M(IMP), and M(AMP) complexes differ by about two to three log units from the present M(PuNTP)2- results, the formation degrees of the macrochelates are astonishingly similar for the two series of nucleotides for a given metal ion and purine-nucleobase residue. The conclusion that N7 of the guanine residue is an especially favored binding site for metal ions is also in accord with observations made for nucleic acids.
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Martin RB. Peptide bond characteristics. METAL IONS IN BIOLOGICAL SYSTEMS 2001; 38:1-23. [PMID: 11219005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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