Arshad Khan
Professional Appointments and Affiliations
Professor of Chemistry, Eberly College of Science and Penn State DuBois
Office
Swift Building, Room 237
Penn State DuBois
1 College Place
DuBois, PA 15801
Education
Ph.D, University of Pittsburgh
Research
1. Theoretical Chemistry:
Determining molecular cluster structure of water & Met-Cars
There is a recent interest in understanding the behavior of extra electrons in various water clusters. Prof. Khan’s prediction (J. Chem. Phys. 2004) that the extra electron can remain within the cage cavity of certain water clusters and may remain on the cage surface of a different type of cluster isomer has already been verified by researchers from California Institute of technology as well as University of California at Berkeley. Prof. Khan is continuing his research in this area with small to large water clusters.
A number of years ago Prof. Khan reported possible structures and stabilities of metal-carbon clusters (met-cars), like Ti8C12 and compounds like Ti14C13 and Ti13C13 on the basis of computational studies (J. Phys. Chem 1993, 1995, Chem. Phys. Lett. 1995). Prof. Castleman and co-workers (met-cars) at Penn State and Prof. Duncan and co-workers (Ti14C13 and Ti13C13) at University of Georgia discovered these new types of metal-carbon compounds. The structures of these compounds are not yet known from an accurate experiment for which extensive experimental and theoretical studies are underway to determine their structures. The other projects involve structure and stability calculations of neutral as well as protonated water clusters with or without guest molecules inside (natural gas hydrates, J. Chem. Phys. 1999, J. Phys. Chem A 2001).
2. Biophysical Chemistry: Theoretical and Experimental Studies
Inactivation mechanism of metallo-enzymes (a-amylase)
The a-amylase is a metallo-enzyme responsible for the hydrolysis of starch to reducing sugars in plants and animals. Prof. Khan and his students already developed a model (Biotechnology Progress 1996, 2016) that describes the effect of heat, calcium binding ligand (like EDTA) and calcium ion concentration on the inactivation rate of this enzyme. At present, they are carrying out relevant experiments (in water as well as water-alcohol mixture) with enzymes from different sources in the presence of additives like caffeine, salts, sugar, acids, and bases. These studies allow one to understand the mechanism of the enzyme inactivation.
Charge transfer through DNA
We theoretically studied charge/hole transfer (CT) reaction through DNA bases (J. Chem. Phys. 2008, Chem. Phys. Lett. 2010, Computational and theoretical Chemistry 2014). These studies suggest that electron withdrawing substituent groups like -NO2, and -COOH attached to Guanine base lowers the activation energy and favors the CT reaction. Among the orientation angles of base pairs (Guanine-Cytosine, GC), the CT is most favored for 0o orientation and has a reduced probability when the angle increases. We hope that these results may have applications in the design of new materials, especially the ones that involve high conducting molecular nanowires.
3. Chemometry/Computational Chemistry to Improve Signal-Noise Ratio
Prof. Khan already developed (Anal. Chem. 1987, 1988) a procedure for every data point smoothing and differentiation by least-squares polynomial filters. The major limitation of this method or any other existing method is, data points from a non-linear function, like gaussian, cannot be reliably smoothed or differentiated. The present interest is to discover a generalized filter function, having both linear and non-linear components, so that data points from linear as well as non-linear functions can be reliably smoothed and differentiated.
4. Unique properties of liquid water and its structure: Theoretical Studies
Water is an unusual liquid with quite a few anomalous properties. These include temperature variation of density, heat capacity at constant pressure, coefficients of expansion, compressibility, etc. A model has been proposed (Chem. Phys. Lett 1997, J. Phys. Chem B 2000) that only considers the presence of bonded as well as broken H-bonds in the liquid and explains the anomalous density variation in liquid H2O. The present interest is to apply the model to explain the other properties of liquid H2O as well as D2O and hence, to establish the model on a firmer ground.
Recent Publications
1. A. Khan, “Liquid Water Model: Predicting Phase Separation and Phase Characteristics” J. Mol. Struct. (Theochem) 755, 161-167 (2005).
2. A. Khan, “Ab initio studies on (H2O)14- clusters: existence of surface and interior-bound extra electrons”, J. Chem. Phys. 125, 024307-1-4 (2006).
3. A. Khan, “Selecting high stability water clusters by examining locations of free OH bonds: application in the study of (H2O)18- clusters”, J. Mol. Struct. (Theochem) 850, 144-151 (2008).
4. A. Khan, “Reorganization and activation energies for hole transfer processes in DNA: a theoretical study”, J. Chem. Phys. 128, 075101 (2008).
5. A. Khan, “Effect of solvent molecules on negative charge development on alpha-carbon of Li-enolate from acetaldehyde: a computational study”, J. Mol. Struct. (Theochem), 895, 127-130 (2009).
6. A. Khan, “Substituent group effects on reorganization and activation energies: Theoretical study of charge transfer reaction through DNA”, Chem. Phys. Lett. 486, 154-159 (2010).
7. A. Khan, “Reorganization, activation and ionization energies for hole transfer reactions through inosine-cytosine, 2-aminopurine—thymine, adenine-thymine, and guanine-cytosine base pairs: A Computational study”, Computational & Theoretical Chemistry, 1013, 136-139 (2013)
8. A. Khan, “Effect of guanine-cytosine base pair orientation and cluster size on ionization energy and charge distribution: A theoretical study”, Computational & Theoretical Chemistry, 1047, 67–70 (2014).
9. M.P. Lundgren, S. Khan, A. K. Baytak and A. Khan, “Fullerene-Benzene purple and yellow clusters: Theoretical and experimental studies”, J. Mol. Struc. 1123, 75-79 (2016).
10. V.T. Calabrese, J. W. Minns, and A. Khan, “Suppression of α-Amylase inactivation in the presence of Ethanol: Application of a two-step model”, Biotechnology Progress 32, 1271-1275 (2016).
11. Neel Rajan, Stephen J. Koellner, Vincent T. Calabrese, and Arshad Khan, “Inactivation of α-Amylase by Caffeine: Reducing the break-down of starch into sugars”, American Journal of Bioscience and Bioengineering, 6(1), 1-4 (2018).
12. A. T. M. G. Sarwar, M. R. Khan and A. Khan, “A quantum mechanical model for hole transport through DNA: Predicting conditions for oscillatory/non-oscillatory behavior”, International Journal of Physics Research and Applications 3, 046-057 (2020).