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The interaction of human hemoglobin with environmental and other gases and molecules is investigated using density functional theory. The investigation includes gases and molecules such as O2, N2, Ar, CO2, H2O, CO, and Cl2. Thermodynamic quantities usually include Gibbs free energy, enthalpy, and entropy. These thermodynamic quantities can be used to distinguish how much strong these molecules are bonded to hemoglobin. The interaction with the two different heme molecules, singlet and triplet states, is shown. Results show that the bonding strength differs greatly between these gases. Most of the investigated molecules remain at their monoatomic, diatomic, or triatomic structure except for O2 and Cl2 that may dissociate into two atoms attached to hemoglobin. The Gibbs free energy of interaction of these atoms and molecules reveals the toxicity of some of these gases, such as CO and Cl2.

Wurtzite nanostructures have been recently described using molecular building blocks called wurtzoids. These wurtzoids are utilized in the present work to describe aluminum mononitride (AlN) nanostructures including its surface doping with group IV elements i.e. C Si, Ge and Sn. Calculations are performed for bare, and hydrogen surface passivated wurtzoids. Results show that hydrogen-passivated (HP) AlN-wurtzoids have energy gaps that are very near to the experimental bulk AlN. Longitudinal optical (LO) vibrational frequencies are also very near to bulk experimental value with blue and red frequency shifting for bare, and hydrogen surface passivated wurtzoids. Doped AlN-wurtzoid2c with group IV elements show a reduction of the energy gap. The gap generally decreases as the atomic number of the dopant increases. The electronic and vibrational properties can be interpreted using the charge transfer between atoms. Minimum atomic charge transfer is for carbon atom doping that leads to a maximum reduction of the energy gap of bare and entirely hydrogen surface passivated wurtzoids. The doped carbon atom charge transfer also induces the highest increase in LO vibrational mode.

Cefepime is a fourth-generation antibiotic with the Stoichiometry C19H24N6O5S2. It is a 1.5 nm molecule. The electronic structure and related spectroscopic properties of cefepime are discussed in the present work. The thermodynamic interaction of the cefepime molecule with water molecules is also discussed. Density functional theory at the B3LYP/6-311G** level is used. Results show good agreement with available structural experimental results such as bond lengths. The iso-electrostatic potential energy shows the position of positive and negative potentials. The HOMO-LUMO energy gap is increased to more than 4 eV due to interaction with water molecules. The highest peak in the experimental IR spectrum (1773 cm−1) is confined between the calculated cefepime highest peak at (1694.4 cm−1) and the hydrated cefepime molecules at (1819-1823 cm−1). Many other evaluated properties such as Raman spectrum, dipole moment, Gibbs free energy, enthalpy, and entropy of interaction with water do not have experimentally measured values. The most stable Gibbs free energy is when cefepime interacts with two H2O molecules.