Willis B. Person

Bio: Willis B. Person is an academic researcher from University of Florida. The author has contributed to research in topics: Infrared spectroscopy & Infrared. The author has an hindex of 41, co-authored 165 publications receiving 6122 citations. Previous affiliations of Willis B. Person include Polish Academy of Sciences.

Matrix isolation studies and ab initio calculations of the vibrational spectra of complexes of water with 3-hydroxypyridine

Abstract: Experimental infrared spectra of a mixture of 3-hydroxypyridine and water in an argon matrix formed by condensation of a gaseous mixture onto a cold window at 15 K exhibit new bands from the two types of 1:1 complexes formed between the two molecules. The vibrational spectra of these complexes are recorded and compared with the spectra of the isolated H 2 O and 3-hydroxypyridine molecules to observe the changes that result from complex formation

CNDO Calculation of Dipole Moment Derivatives and Infrared Intensities of C6H6 and C6F6

Abstract: The dipole moment derivatives of C6H6 and C6F6 have been calculated using the complete neglect of differential overlap (CNDO) approximate molecular orbital theory. The calculated set of derivatives with respect to the symmetry coordinates (∂ p/∂ Sj) for the e1u species of C6H6 agrees remarkably well with the unique experimental set of derivatives determined from infrared intensity measurements and the normal coordinate analysis for C6H6 and its deuterated analogues. The success of the benzene calculation suggests that we may have confidence in the CNDO results for C6F6, even though the agreement with the experimental results is much worse. An analysis of the ∂ p/∂ Sj values is given in terms of bond moment derivatives. The failure of the CNDO theory to predict a sufficiently large ``rehybridization moment'' to explain the observed intensity difference between in‐plane and out‐of‐plane bending vibrations is discussed.

Preliminary interpretation of the infrared intensities of combination and difference bands of N2O and CO2.

Abstract: Expressions derived by Overend for the infrared absorption of combination and difference bands are tested against experimental data for N2O and CO2(ν3±ν1, ν3±ν2, and ν1±ν2, where data are available). From these comparisons, values of the electrical anharmonicities Pαss′(=∂2pα /∂qs∂qs′) are obtained. Overend’s prediction of an anomalously higher value for the transition moment of certain difference bands than for the corresponding combination bands is verified. For CO2, mechanical anharmonicity dominates the intensities perdicted for combination and difference bands; for N2O, electrical anharmonicity is comparable in its contribution to the intensities of combination and difference bands.

Calculation of the Vibrational Intensities of F2CO

Abstract: The CNDO/2 calculations of the dipole‐moment derivatives with respect to the vibrational symmetry coordinates of F2CO, ∂p / ∂Sj, are carried out in order to determine which of the possible sets of values found from the experimental intensity data is most likely to be correct. Reasonable agreement is obtained with one of the many sets of values and an unambiguous assignment is possible. The signs of the dipole‐moment derivatives with respect to the normal coordinates are thereby fixed. The inadequacy of the bond‐moment model for the vibrational intensities of this molecule is discussed.

Bioceramics: From Concept to Clinic

Abstract: Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.

Bioceramics : from concept to clinic

Abstract: Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.

How Well Does a Restrained Electrostatic Potential (RESP) Model Perform in Calculating Conformational Energies of Organic and Biological Molecules

Abstract: In this study, we present conformational energies for a molecular mechanical model (Parm99) developed for organic and biological molecules using the restrained electrostatic potential (RESP) approach to derive the partial charges. This approach uses the simple "generic" force field model (Parm94), and attempts to add a minimal number of extra Fourier components to the torsional energies, but doing so only when there is a physical justification. The results are quite encouraging, not only for the 34-molecule set that has been studied by both the highest level ab initio model (GVB/LMP2) and experiment, but also for the 55-molecule set for which high-quality experimental data are available. Considering the 55 molecules studied by all the force field models for which there are experimental data, the average absolute errors (AAEs) are 0.28 (this model), 0.52 (MM3), 0.57 (CHARMm (MSI)), and 0.43 kcal/mol (MMFF). For the 34-molecule set, the AAEs of this model versus experiment and ab initio are 0.28 and 0.27 kcal/mol, respectively. This is a lower error than found with MM3 and CHARMm, and is comparable to that found with MMFF (0.31 and 0.22 kcal/mol). We also present two examples of how well the torsional parameters are transferred from the training set to the test set. The absolute errors of molecules in the test set are only slightly larger than in the training set (differences of <0.1 kcal/mol). Therefore, it can be concluded that a simple "generic" force field with a limited number of specific torsional parameters can describe intra- and intermolecular interactions, although all comparison molecules were selected from our 82-compound training set. We also show how this effective two-body

An all atom force field for simulations of proteins and nucleic acids.

Abstract: We present an all atom potential energy function for the simulation of proteins and nucleic acids. This work is an extension of the CH united atom function recently presented by S.J. Weiner et al. J. Amer. Chem. Soc., 106, 765 (1984). The parameters of our function are based on calculations on ethane, propane, n−butane, dimethyl ether, methyl ethyl ether, tetrahydrofuran, imidazole, indole, deoxyadenosine, base paired dinucleoside phosphates, adenine, guanine, uracil, cytosine, thymine, insulin, and myoglobin. We have also used these parameters to carry out the first general vibrational analysis of all five nucleic acid bases with a molecular mechanics potential approach.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.