منابع مشابه
Tunnelling in carbonic acid.
The cis,trans-conformer of carbonic acid (H2CO3), generated by near-infrared radiation, undergoes an unreported quantum mechanical tunnelling rotamerization with half-lives in cryogenic matrices of 4-20 h, depending on temperature and host material. First-principles quantum chemistry at high levels of theory gives a tunnelling half-life of about 1 h, quite near those measured for the fastest ro...
متن کاملAqueous carbonic acid (H2CO3).
Carbonic acid (H2CO3) is a molecule right at the interface between organic and inorganic chemistry. In fact, according to some definitions it is an organic molecule, while according to others it is an inorganic molecule. Its exceptionality can also be recognized from the fact that it formally belongs neither to the mononor dicarboxylic acids, even though it is a C1 diprotic acid. The diprotic n...
متن کاملDensity functional study of carbonic acid clusters
Density functional calculations on carbonic acid H2CO3 are extended to clusters of up to five such units. The most stable forms are the linear, hydrogen-bonded analogs of the dimer with anti–anti orientation. We calculate structures and vibration frequencies, as well as the energy required to bend and stretch the linear isomers. Linear chains of up to ;20 units should be favored over ring struc...
متن کاملAcid Difference Spectra of Human Carbonic Anhydrases.
Human carbonic anhydrase B loses enzymatic activity as it undergoes an irreversible conformational change near pH 4 (1). Riddiford (2) further found that seven of the eleven histidyl groups, which are unreactive in the native protein, become titratable during this change. Also, five or six of the eight tyrosyl groups do not ionize freely and reversibly in the native protein (2, 3). Human carbon...
متن کاملThe interconversion of glutamic acid and aspartic acid in respiring tissues.
We wish to thank Professor Sir Hans A. Krebs, F.R.S., for his interest and encouragement and Mrs M. Jenkins for her skilled technical assistance. This work was supported by the Rockefeller Foundation and by the Office of Scientific Research of the Air Research and Development Command of the United States Air Force, through its European Office, under contract no. AF. 61(052)-180, and was done wh...
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ژورنال
عنوان ژورنال: The Lancet
سال: 1838
ISSN: 0140-6736
DOI: 10.1016/s0140-6736(02)82761-1