@article{KalliesMeier2001,
  author    = {Kallies, Bernd and Meier, R.},
  title     = {The electronic structure od 3 [M(H20)6)3+ions from Sc(III)till Fe (III) : a quantum mechanical study based on DFT computations and natural bond orbital analyses},
  year      = {2001},
  language  = {en}
}
@article{KalliesMitzner1998,
  author    = {Kallies, Bernd and Mitzner, Rolf},
  title     = {Structural Properties of Protonated Acyl Derivatives as Studied by Quantum Mechanics},
  year      = {1998},
  abstract  = {Basicities of 16 acyl compounds including selected aldehydes, ketones, esters, amides and ureas in the gas phase and in water were calculated with the Becke3LYP/6-31G* method. Solvent effects were modeled using a polarizable electrostatic continuum representation of the solvent. The properties of the electron densities of protonated molecules were described by localized bond orbitals. Our results suggest that the carbonyl oxygen is the preferred site of protonation for all molecules studied. Calculated pKa values in water range from -12 for aldehydes to + 1.5 for ureas. They agree well with published experimental data. We found that a high basicity of acyl compounds at the carbonyl oxygen is coupled with a large amount of additional resonance stabilization at the carbonyl group. The protonation of the leaving group of eaters, amides and ureas is less preferred, but the basicity difference between C=O and -OR or -NR2 decreases from esters to ureas. Calculated pKa values for this site range from -18 for esters to + 3 for ureas. These values are often not accessible by experiment. The structure of carboxylic acid derivatives protonated at the leaving group is determined by prefragmentation of the molecules into an acylium ion or positively charged isocyanate and an alcohol or amine. (C) 1998 Elsevier Science B.V.},
  language  = {en}
}
@article{KalliesMitzner1998,
  author    = {Kallies, Bernd and Mitzner, Rolf},
  title     = {Models of water-assisted hydrolyses of methyl formate, formamide, and urea from combined DFT-SCRF calculations},
  year      = {1998},
  abstract  = {In this work we present theoretical studies of the hydrolytic reaction of methyl formate, formamide and urea with one water molecule. The studied systems contain two additional water molecules which can act as bifunctional acid- base catalysts. These water molecules catalyze proton transfers between the primary reacting species. Our models describe the concerted transfer of two protons in every reaction step. The calculations have been carried out with the Becke3LYP/6-31G* method. Unspecific solvation effects have been included by means of a polarizable continuum model. Substrate reactivity differences as well as preferences for different reaction pathways can be discussed with the aid of these molecular systems. The studied alternative mechanisms include the common addition-elimination mechanism via a tetrahedral intermediate, and a concerted SN-like mechanism without a reaction intermediate. Our results suggest that the proved decreasing substrate reactivity in the order ester, amide, urea is caused by a rising resonance stabilization of the reaction centre, and not by a different positive partial charge of the carbonyl carbon. It is also concluded, that the probability of a concerted addition of a nucleophile and elimination of a leaving group without a tetrahedral intermediate rises in the order ester, amide, urea. The ordering of reactivity is not influenced by this behaviour.},
  language  = {en}
}
@article{KalliesKunzKlausetal.2000,
  author    = {Kallies, Bernd and Kunz, Iris and Klaus, Susanne and Schorr, Ulrike and Sharma, Arya M.},
  title     = {Kinetic analysis of the thermic effect of food and its relationship to body composition in humans},
  year      = {2000},
  abstract  = {The course of energy expenditure after a meal can vary widely with regard to the slope of onset, amplitude, and duration of the thermic effect. The aim of the present study was to explore the relationship between the thermic effect of food (TEF), as characterized by kinetic analysis of postprandial energy expenditure, body composition, and variables related to the metabolic syndrome including central obesity, hypertension, and glucose tolerance. A total of 181 men and women (body mass index [BMI] range, 19.4 to 52.2 kg/m2) were characterized for body composition, blood pressure, oral glucose tolerance, and energy expenditure after a test meal. Energy expenditure, as measured by indirect calorimetry, was analyzed over a 6-hour period by 3-parameter curve fitting using equations derived from kinetics describing a biphasic reaction involving 2 consecutive first-order reactions (A->B->C). Apart from total thermic effect of food (TEFk), the curve also provided an estimate of time of peak (Tp) and amplitude of peak (Ap) for each subject. Multiple stepwise regression analysis with TEFk, Ap, and Tp as dependent variables showed significant effects of sex, age, body weight, body fat, -blockade, and body composition on TEF curve parameters. Cluster analysis based on Tp shown 2 distinct clusters with significant differences in age and body fat mass. This study shows that kinetic analysis of postprandial energy expenditure can be used to examine the determinants of the time course of the thermic effect of food in man.},
  language  = {en}
}
@article{BeitzLaudienLoehmannsroebenetal.2006,
  author    = {Beitz, Toralf and Laudien, Robert and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Kallies, Bernd},
  title     = {Ion mobility spectrometric investigation of aromatic cations in the gas phase},
  issn      = {1089-5639},
  doi       = {10.1021/Jp055335n},
  year      = {2006},
  abstract  = {In this work, ion mobility (IM) spectra of more than 50 aromatic compounds were recorded with a laser-based IM spectrometer at atmospheric pressure. IM spectra of PAH in the laser desorption experiment show a high complexity resulting from the occurrence of monomeric, dimeric, and oligomeric cluster ions. The mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omega(calc)) on the basis of the exact hard sphere scattering model and their comparison with the experimentally determined diffusion cross sections (Omega(exp)). Extended Omega(exp)/Omega(calc) and Omega(exp/)mass correlations were performed in order to gain insight into conformational properties of cationic alkyl benzenes and internal rotation of phenyl rings in aromatic ions. This is demonstrated with some examples, such as the evaluation of the dihedral angle of the ions of 9,10- diphenylanthracene, o- and m-terphenyl, and 1,2,3- and 1,3,5-triphenylbenzene. Furthermore, sandwich and T-structures of dimeric PAH cations are discussed. The analysis was extended to oligomeric ions with up to nine monomer units. Experimental evidence is presented suggesting the formation of pi-stacks with a transition toward modified pi-stacks with increasing cluster size. The distance between monomeric units in dimeric and oligomeric ions was obtained},
  language  = {en}
}
@article{KalliesKochMitzner1997,
  author    = {Kallies, Bernd and Koch, Andreas and Mitzner, Rolf},
  title     = {Competitive resonance at the carbonyl group as visualized by the natural bond orbital analysis},
  year      = {1997},
  language  = {en}
}