Maciej Gutowski

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Finding the most stable tautomer or a set of low-energy tautomers of molecules is critical in many aspects of molecular modelling or virtual screening experiments. Enumeration of low-energy tautomers of neutral molecules in the gas-phase or typical solvents can be performed by applying available organic chemistry knowledge. This kind of enumeration is(More)
We describe a procedure of finding low-energy tautomers of a molecule. The procedure consists of (i) combinatorial generation of a library of tautomers, (ii) screening based on the results of geometry optimization of initial structures performed at the density functional level of theory, and (iii) final refinement of geometry for the top hits at the(More)
The possibility of electron binding to the HNNH 3 and H 2 NNH 2 tautomers of hydrazine was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations. The HNNH 3 tautomer, with a dipole moment of 5.4 D, binds an electron by 1076 cm-1 whereas the H 2 NNH 2 tautomer forms neither a dipole-nor valence-bound anionic(More)
Using helium cluster-isolation spectroscopy we have prepared and characterized the lowest quartet state (1 4 A 0 2) of the sodium trimer. Upon excitation to the 2 4 E 0 electronic state, laser induced fluorescence excitation and emission spectra have been obtained. With the aid of ab initio calculations, the spectra have been vibronically assigned and new(More)
The relative stabilities of zwitterionic and canonical forms of neutral arginine and of its protonated derivative were studied by using ab initio electronic structure methods. Trial structures were first identified at the PM3 level of theory with use of a genetic algorithm to systematically vary geometrical parameters. Further geometry optimizations of(More)
Even a relatively small molecule with 10-20 atoms might have a few local minima, which correspond to different conformers. The number of local minima quickly increases with molecular size and the most common algorithms, driven by calculated forces, frequently identify a minimum, which is closest to the initial structure, rather than the most stable(More)
Energies of different conformers of 22 amino acid molecules and their protonated and deprotonated species were calculated by some density functional theory (DFT; SVWN, B3LYP, B3PW91, MPWB1K, BHandHLYP) and wave function theory (WFT; HF, MP2) methods with the 6-311++G(d,p) basis set to obtain the relative conformer energies, vertical electron detachment(More)
When plotting different orbitals with consistent contour values, one can create illusions about the relative extension of charge distributions. We suggest that the comparison is not biased when plots reproduce the same fraction of the total charge. We have developed an algorithm and software that facilitate this type of visualization. We propose(More)
In contrast to widely familiar acid-base behavior in solution, single molecules of NH3 and HCl do not react to form the ionic salt, NH+4Cl-, in isolation. We applied anion photoelectron spectroscopy and ab initio theory to investigate the interaction of an excess electron with the hydrogen-bonded complex NH3...HCl. Our results show that an excess electron(More)
Recently, we reported the discovery of adiabatically bound anions of guanine that might be involved in the processes of DNA damage by low-energy electrons and in charge transfer through DNA. These anions correspond to some tautomers that have been ignored thus far. They were identified using a hybrid quantum mechanical-combinatorial approach in which an(More)