Herzberg studies

C. C. Chen, O. Herzberg, Inhibition of beta-Lactamase by Clavulanate. Trapped Intermediates in Cryocrystallographic Studies , J. Mol. Biol. 1992, 224, 1103-1113. 

The C state has attracted much attention from spectroscopists because the state was believed to be the upper state of the ultraviolet absorption band which can help establish the accurate dissociation energy of the ground state of H2 [82]. Therefore, several attempts have been made to obtain the complete PEC for the C state [53,76,83,84]. The calculations by Browne revealed that there exists a suspicious maximum at i = 8a.u. which is about 160 cm above the dissociation limit [76]. This observation was consistent with the conclusion of Herzberg and Monfils that a maximum might exist in the vicinity of / — 13 a.u. [82]. The subsequent calculations by Kolos and Wolniewicz [53], and Namioka [77] refined the barrier to be about 105.5 cm at i = 9 a.u. The computed PEC for the C state and the fitted spectroscopic parameters (r, v, v Xe, a ) in the present study agree well with the experiment, as demonstrated by Table 8. 

Magnesium is also of interest as a replacement for Ca(ll) in calcium-requiring enzymes. In some of these, the replacement is simple (Lewinski and Lebioda, 1986), and in others it cannot occur. NMR studies show that magnesium can bind in the calcium sites of troponin C (Tsuda et al., 1990). The structure of turkey skeletal muscle troponin C has recently been reported (Herzberg and James, 1985). In one domain the replacement of Ca(II) by Mg(II) causes a conformational change, but in the other domain it does not. 

The Gap Test, sometimes called Barrier Test or Booster Test, was first suggested by H. Muraour in MAF 12, 559(1933), but the first systematic study of the phenomenon was done by G. Herzberg R. Walker, Nature 161, 647(19-48). Since that time many expls labs both in the US and abroad have adopted and standardized it as a practical test of sensitivity. The apparatus used by... 

Information about the structure of gas molecules haB been obtained by several methods. Spectroscopic studies in the infrared, visible, and ultraviolet regions have provided much information about the simplest molecules, especially diatomic molecules, and a few polyatomic molecules. Microwave spectroscopy and molecular-beam studies have yielded very accurate interatomic distances and other structural information about many molecules, including some of moderate complexity. Molecular properties determined by spectroscopic methods are given in the two books by G. Herzberg, Spectra of Diatomic Molecules, 1950. and Infrared and Raman Spectra, 1945, Van Nostrand Co., New York. The information obtained about molecules by microwave spectroscopy is summarised by C. H. Townes and A. L. Schawlow in their book Microwave Spectroscopy of Gases, McGraw-Hill Book Co., New York, 1955. 

In spite of many studies the complete analysis of the ultraviolet absorption spectrum has not been successful [Herzberg (16), p. 511]. The spectroscopy and photochemistry of S02 may be conveniently discussed for four... 

The formation of ozone in the Herzberg System (3) 2 + - 32 , has been studied by Warburg (100). The results are summarized in Table I. It should be emphasized that the results at 125 and 300 kg./cm.2 pressure were obtained in earlier experiments by Warburg (99). 

The internal motion of a polyatomic molecule is rather complex. In order to understand its principles, it is convenient and customary to refer to the vibration of a diatomic molecule. The internal motion in molecules has above all been studied experimentally and theoretically by spectroscopists. The approach towards the study of polyatomic molecules through diatomic molecules has been excellently demonstrated by the two classical books of G. Herzberg, the first one dealing with diatomic molecules2, the second one with polyatomic molecules3). Although these two books should by now be hopelessly out of date, and in spite of the fact that they have been succeeded by a series of up to date works, they can still be recommended to to-day s students. 

The lifetimes and kinetic behavior of many triplet states of molecules, particularly of aromatic compounds, have been studied by Porter and his coworkers. The identification of the absorption spectra of methyl radicals, of HCO radicals and of NH2 radicals, mainly in Herzberg s laboratory at Ottawa, has permitted flash photolysis to be used directly to measure the rates of radical reactions. 

The principles of electronic spectroscopy have been discussed by Herzberg (1950) for diatomic molecules, and in a classic review by Sponer and Teller (1941) for the more general case of polyatomic structures. Recent developments are described in articles appearing regularly in the Annual Reviews of Physical Chemistry. Triatomic molecules and radicals have been intensively studied, the latter by the powerful method of flash photolysis (Herzberg, 1959). As triatomic structures have been comprehensively reviewed recently (Ramsay, 1962) we include in this article only those triatomic systems that are of particular interest in organic chemistry. Otherwise attention will be directed to molecules of four or more atoms, including all known representatives of the important chromophores. 

Herzberg 1979), very few studies of these latter two gas phase species have appeared nonetheless, they are reported to be important for condensed phase chemistry (Platz 1990 Schuster 1986). Characterization of their unsolvated, solvated, and reacting properties and energy levels is certainly a useful endeavor. Parallel calculations at a high ab initio level can also shed light on the properties (i.e., geometry, electronic and vibrational energy levels, solvation structures and reactions) of reactive intermediates. 

The radicals that have been investigated in the gas phase are listed by Jacox (1984, 1988, 1990), Miller (Foster and Miller 1989), and Huber (Huber and Herzberg 1979). Solvated systems have also been studied and have been reviewed by Heaven (Heaven 1992) and Lester (Giancarlo et al. 1994). The cluster chemistry studies, as such, are discussed below for benzyl (C6H5CH2 ) and methyl radicals. Work in progress on small radicals, carbenes, and nitrenes will be briefly mentioned at the end of the section. 

Fig. 13.4 Definition of temperatures relevant to hydrological studies Ti = average temperature in the rainy season at recharge area T2 = average annual temperature at recharge area T3 = temperature at the base of the aerated zone, above the water table (deduced from the Ar, Kr, and Xe concentrations) T4 = maximum temperature reached at the deepest point of the water path T5 = observed spring or well temperature at the time of sampling T6 = ambient air temperature at the time of sampling. (From Herzberg and Mazor, 1979.)...

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