Dr. Arshad Khan, Professor of Chemistry

Arshad Khan, Professor of Chemistry

Penn State Eberly College of Science,

Penn State DuBois Campus


kub@psu.edu



Dr. Arshad Khan's Research Interests


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 studies1.  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 clusters2 with or without guest molecules inside (natural gas hydrates).

 

2. Polymer Chemistry: Theoretical and Experimental Studies

Iodine complexes are well known for their anti-microbial properties.  In addition, molecular iodine is known to cure certain types of lumps in the female breast.  The complex that carries molecular iodine has been seriously considered for the development of a drug.  Prof. Khan and his students successfully characterized iodine complexes with water3, methanol, ethanol, acetone4, and starch5 by applying both theoretical and experimental methods.  The above studies suggest that the iodide ions are not directly involved in the iodine complex formation and thus, contradict the commonly believed mechanism of the complex formation.

     The recent interest is to study interaction of iodine with cyclodextrins.  Since cyclodextrins form host-guest type complexes, these studies followed by structure calculations may lead to the discovery of new complexes with unique properties.

 

3. 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 different reducing sugars in plants and animals.  Prof. Khan and his students already developed a model6 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 salts, sugar, acids, and bases.  These studies will allow one to verify the model and hence, to understand the mechanism of the enzyme inactivation.

 

4. Chemometry/Computational Chemistry to Improve Signal-Noise Ratio

Prof. Khan already developed7, 8 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 due to the fact that the 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.

 

5. 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 proposed9,10 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.

 

References

1. a) Khan, A.; J. Phys. Chem.  97, 10937 (1993).

    b) Khan, A.; J. Phys. Chem.  99, 4923 (1995).

    c) Khan, A.; Chem. Phys. Lett.  247, 447 (1995).

2. a) Khan, A.; Chem. Phys. Lett.  217, 443 (1994).

    b) Khan, A.; J. Phys. Chem.  99, 12450 (1995).

    c) Khan, A.; Chem. Phys. Lett.  253, 299 (1996), 258, 574 (1996).

    d) Khan, A.; J. Phys. Chem.  106 (13), 5537 (1997).

    e) Khan, A.; J. Chem. Phys.  110 (24), 11884 (1999).

3. Fonslick, J., Khan, A. & Weiner, B.; J. Phys. Chem.  93, 3836 (1989).

4. Khan, A.; J. Chem. Phys.  96, 1194 (1992).

5. a) Minick, M., Fotta, K. & Khan, A.; Biopolymers  31, 57 (1991).

    b) Fonslick, J. & Khan, A.; J. Polym. Chem.  27, 4161 (1989).

    c) Davis, H. & Khan, A.; J. Polym. Chem.  32, 2257 (1994).

    d) Davis, H., Skrzypek, W. & Khan, A.; J. Polym. Chem.  32, 2267 (1994).

    e) Calabrese, V. T. & Khan, A.;  J. Polym. Chem. 37, 2711 (1999).

    f) Calabrese, V. T. & Khan, A.;  J. Phys. Chem. 104, 1287 (2000).

6. a) Khan, A.; Abstract of papers #106, Division of Microbial and Biochemical                  

        Technology, 198th ACS Meeting at Miami Beach, FL, Sept. 10-15, 1989.

    b) Lecker, D. & Khan, A.; Biotechnology Progress  12, 713 (1996).

    c) Lecker, D. & Khan, A.; Biotechnology Progress, 14, 621 (1998).

7. Khan, A.; Anal. Chem.  59, 654 (1987). 

8. Khan, A.; Anal. Chem.  60, 369 (1988).

9. Khan, A.; Khan, R.; Khan, M. F.; Khanam, F.; Chem. Phys. Lett.  266, 473 (1997).

10. Khan, A.; J. Phys. Chem. B 104, 11268 (2000).

 


Verification of research predictions

a)  Two recent Science papers by a group from Japan (Science, vol 304, page 1134, 2004) and three groups from USA (Yale, Pittsburgh & Georgia, Science, vol 304, page 1137, 2004) suggest that my predicted structures of (H2O)20H+ and (H2O)21H+ clusters are probably correct (A. Khan, Chem. Phys. Lett. 319, 440, 2000).

 

 b) In Oct 22, 2004 issue of Science, Professor Zewail (Nobel Laureate) and co-workers at California Institute of technology & Prof. Neumark and co-workers at Berkeley (in a second paper) reported experimental results confirming my prediction (A. Khan, J. Chem. Phys. 121, 280, 2004)) that an extra electron in (H2O)24- cluster is within the cavity of one type of cluster isomer and on the surface in a second type of isomer (D. M. Neumark and co-workers, Science 307, 93, 2005).

 

c) In February 15 issue of the Journal of Chemical Physics (vol 122, 2005), 4 groups of scientists from Taiwan, China, Singapore and USA (University of Pennsylvania) through experimental and theoretical studies verified my prediction that in (H2O)20H+ cluster a neutral molecule of water is in the cavity of dodecahedral cluster and the positive ion is on the cage surface.

 

Citations in Text Books  

Our results on starch-iodine composition have been discussed in several editions of an analytical chemistry textbook used extensively in many universities at the Junior and Senior levels.

Title of the book: Quantitative Chemical Analysis, 7th edition (2007).

            Editor: D. C. Harris

The paper that was cited on page 335:

V. T. Calabrese and A. Khan, “Amylose-iodine complex formation without KI: Evidence for absence of iodide ions within the complex”, J. Polym. Sc. A.  37 (15), 2711 (1999).

 

Title of the book: Quantitative Chemical Analysis, 6th edition (2003).

            Editor: D. C. Harris

The paper that was cited on page 356:

H. Davis, W. Skrzypk, and A. Khan, J. Polymer Sci., A32, 2267 (1994).

 


 

 Publications 

1. A. Khan, H. R. Siddiqui and P. E. Siska, XII International Conference on the Physics of Electronics and Atomic Collisions,  Gatlinburgh, Tennessee, USA, 1981, abstract of papers, p. 508.

 2. A. Khan, H. R. Siddiqui, D. W. Martin and P. E. Siska, “Crossed beam measurement of the H+ velocity-angle distribution from He*     (21S) + H Penning ionization”, Chem. Phys. Lett.  84, 280 (1981).

 3. A. Khan and M. M. Huque, “Study of acid catalyzed acetamide hydrolysis in different dielectric media”, Bangladesh J. Sci. Ind. Res.     16, 109 (1981).

 4. H. R. Siddiqui, A. Khan and P. E. Siska, “Possible systematic error in molecular beam time-of-flight analysis with quadruple mass      spectrometer”, Rev. Sci. Instrum.  53, 1940 (1982).

 5. A. Khan and K. D, Jordan, “Theoretical Potential Energy curves and Specroscopic properties of the X2Su+ and A2Sg+ states of   He2+ ”, Chem. Phys. Lett.  128, 368 (1986).

 6. A. Khan, “Problems of Smoothing and Differentiation of data by Least Squares Procedures and Possible Solutions”, Anal. Chem.  59, 654 (1987).

 7. A. Khan, “Procedure for increasing the accuracy of the data point slope estimation by least squares polynomial filters”, Anal. Chem.  60, 369 (1988).

 8. J. Fonslick, A. Khan and B. Weiner, “On the question of hypoiodite ion formation in the aqueous solution of iodine: Theoretical and experimental study of H2OI2 complex.”, J. Phys. Chem.  83, 3836 (1989).

 9. J. Fonslick and A. Khan, “Thermal stability and composition of the amylose-iodine complex”, J. Polym. Sc. A  27, 4151 (1989).

 10. M. Minick, K. Fotta and A. Khan, “Polyiodine units in starch-iodine complex”, Bioploymers  31, 57 (1991).

 11. A. Khan, H. R. Siddiqui and P. E. Siska, “Angle-energy distributions of Penning ions in crossed molecular beams.  I. Evidence for discrete nonadiabaticity in the He*(21S) + H, D ® He + H+, D+ + e- reaction”, J. Chem. Phys.  94, 2588 (1991).

 12. A. Khan, H. R. Siddiqui and P. E. Siska, “Angle-energy distributions of Penning ions in crossed molecular beams.  II. Effect of Penning electron recoil in Ne*(3s3P2) + H, D ® Ne + H+, D+ + e- ”, J. Chem. Phys.  95, 3371 (1991).

 13. A. Khan, “Theoretical studies of the complexes of iodine with methanol, ethanol, and acetone”, J. Chem. Phys.  96, 1194 (1992).

 14. A. Khan, “Theoretical studies of the structures of Ti8C12+ cluster: Existence of C12 cage surrounded by metal atoms”, J. Phys. Chem.  97, 10937 (1993).

 15. A. Khan, “Theoretical studies of the clathrate structures of (H2O)20, H+(H2O)20 and H+(H2O)21 .”, Chem. Phys. Lett.  217, 443 (1994).

 16. H. Davis and A. Khan, “Determining the chromophore in the amylopectin-iodine complex by theoretical and experimental studies”, J. Polym. Sc. A:  32, 2257 (1994).

 17. H. Davis, W. Skrzypek and A. Khan, “Iodine binding by amylopectin and stability of the ampylopectin-iodine complex”, J. Polym. Sc. A:  32, 2267 (1994).

 18. A. Khan, “Isomers of neutral Ti met-car: A theoretical study”, J. Phys. Chem.  99, 4923 (1995).

 19. A. Khan, “Examining the cubic, fused cubic and caged structures of (H2O)n for n=8, 9, 12, 16, 20 and 21: Do fused cubic structures form? ”, J. Phys. Chem.  99, 12450 (1995).

 20. A. Khan, “Theoretical studies of face centered cubic (FCC) Ti14C13+ and Ti13C13+ clusters: Can Met-cars form from these FCC structures?”,  Chem. Phys. Lett.  247, 446 (1995).

 21. A. Khan, “Theoretical studies of tetrakaidecahedral structures of water clusters (H2O)24, (H2O)27 and (H2O)28 pentakaidecahedral clusters”, Chem. Phys. Lett.  253, 299 (1996).

 22. A. Khan, “Theoretical studies of structures and stabilization energies of (H2O)26, (H2O)27 and (H2O)28 pentakaidecahedral clusters”, Chem. Phys. Lett.  258, 574 (1996).

 23. S. Kumari, A. Roman, A. Khan, “Chromophore and spectrum of the glycogen-iodine complex”, J. Polym. Sc. A 34, 2975 (1996).

 24. D. N. Lecker and A. Khan, “Theoretical and experimental studies of the effect of heat, EDTA and enzyme concentrations on the inactivation rate of a-amylase from bacillus species”, Biotechnology Progress  12, 713 (1996).

 25. A. Khan, R. Khan, M. F. Khan and F. Khanam, “A cluster model explaining quantitatively the anomalous variation of density of water with temperature”, Chem. Phys. Lett.  266 (5/6), 473 (1997).

 26. A. Khan, “Theoretical studies of large water clusters: (H2O)28, (H2O)29, (H2O)30 and (H2O)31 hexakaidecahedral structures”, J. Chem. Phys.  106 (13), 5537 (1997).

 27. S. Kumari, D. N. Lecker and A. Khan, “Interaction of iodine species with glycogen at high concentrations of iodine”, J. Polym. Sc. A 35, 927 (1997).

 28. D. N. Lecker, S. Kumari and A. Khan, “Iodine binding capacity and iodine binding energy of glycogen”, J. Polym. Sc. A 35, 1409 (1997).

 29. A. Khan, “Gas phase pure water clusters: Dodecahedral to Hexakaidecahedral clusters”, in Recent Research Developments in Physical Chemistry, 1, 333 (1997), Ed: S. G. Pandalai, Transworld Research Network, T. C. 36/248 (1), Trivandrum-695 008, India (invited paper).

 30.  A. J. Barret, K. L. Barret and A. Khan, “Effects of acetone, ethanol, isopropanol, and dimethyl sulfoxide on the starch-iodine complex formation”, Journal of Macromolecular Science- Pure and Applied Chemistry A 35 (5), 711 (1998), corrected version: 35 (10), 1603 (1998).

 31. D. N. Lecker and A. Khan, “Model for inactivation of a-amylase in the presence of salts: Theoretical and experimental studies”, Biotechnology Progress 14 (4), 621 (1998).

 32. A. Khan, “Carbohydrate-iodine complexes”, in Recent Research Developments in Physical Chemistry, 2, 889 (1998), Transworld Research Network, T. C. 36/248 (1), Trivandrum-695 008, India (invited paper).

 33. A. Khan, “Theoretical Studies of Large (H2O)32-35 Clusters”, J. Phys. Chem. A. 103, 1260 (1999).

 34. V. T. Calabrese and A. Khan, “Amylose-iodine complex formation without KI: Evidence for absence of iodide ions within the complex”, J. Polym. Sc. A.  37 (15), 2711 (1999).

 35. A. Khan, “Theoretical Studies of CH4(H2O)20, (H2O)21, (H2O)20 and fused dodecahedral and tetrakaidecahedral structures: How do natural gas hydrates form?” J. Chem. Phys. 110 (24), 11884 (1999).

 36. V. T. Calabrese and A. Khan, “Polyiodine and polyiodide species in aqueous solution of iodine + KI: Theoretical and Experimental Studies”, J. Phys. Chem. A. 104, 1287 (2000).

 37. A. Khan, “Ab initio studies of (H2O)20H+ and  (H2O)21H+ prismic, fused cubic and dodecahedral clusters: can H3O+ ion remain in cage cavity?”, Chem. Phys. Lett. 319, 440 (2000).

 

38. A. Khan, “A liquid water model: density variation from supercooled to superheated states, prediction of H-bonds and temperature limits”, J. Phys. Chem. B. 104, 11268 (2000).

 

39. A. Khan, M. R. Khan, M. F. Khan and F. Khanam, “A liquid water model that explains the variation of surface tension of water with temperature”, Japanese Journal of Applied Physics 40, 1467-1471 (2001).

 

40.  A. Khan, “Theoretical studies of NH4+(H2O)20 and NH3(H2O)20H+ clusters”, Chem. Phys. Lett. 338 (2/3), 201-207 (2001).

41. A. Khan, “Stabilization of hydrate structure H by N2 and CH4 molecules in 435663 and 512 cavities, and fused structure formation with 51268 cage: A theoretical study”, J. Phys. Chem. A. 105, 7429 (2001).

42. A. Khan, “Ab initio studies of (H2O)28 hexakaidecahedral cluster with Ne, N2, CH4 and C2H6 guest molecules in the cavity”, J. Chem. Phys. 116, 6628 (2002).

43. J. W. Minns and A. Khan, α-Cyclodextrin-I3- host-guest complex in aqueous solution: Theoretical and Experimental Studies”, J. Phys. Chem. A. 106, 6421 (2002).

44. A. Khan, “Solvated electron in (H2O)20- and (H2O)21- clusters: A theoretical study”, J. Chem. Phys. 118, 1684 (2003).

45.  A. Khan, “Ab initio studies of CO2(H2O)20,24,28 clusters: Role of CO2 in hydrate formation”, J. Mol. Struct. (Theochem). 664, 237 (2003).

46.  A. Khan, “Theoretical studies of Na(H2O)19-21+ and K(H2O)19-21+ clusters: explaining the absence of magic peak for Na(H2O)20+”, Chem. Phys. Lett. 388, 342-347 (2004).

47. A. Khan, "Extra electron in (H2O)24- cluster isomers: A theoretical study”, J. Chem. Phys. 121, 280 (2004).

48. A. Khan, M. R. Khan, M. F. Khan and F. Khanam, “Liquid water Model: Anomalous density variation of liquid D2O and shifting of density maximum under pressure”, J. Mol. Struct. (Theochem). 679, 165-170 (2004).

49. V. T. Calabrese and A. Khan, “Stabilization of alpha-amylase in presence of sugars:  Validity of a two-step inactivation model”,  Recent Res. Devel. Chem. Phys. 5, 303-315 (2004), Transworld Research Network 37/661(2), Fort P. O., Trivandrum 695 023, Kerala, India.  (invited contribution to a book)

50.  A. Khan, “Solvated electron in (H2O)20- dodecahedral cavity: calculated stretch frequencies and vertical dissociation energy” Chem. Phys. Lett. 401, 85-88 (2005).

51.  A. Khan, “Theoretical studies of Li (H2O)19+,  Li (H2O)20+ and  Li (H2O)21+ clusters”, Chem. Phys. Lett.  408, 71-74 (2005).

52.  A. Khan, “Liquid Water Model: Predicting Phase Separation and Phase Characteristics” J. Mol. Struct. (Theochem) 755, 161-167 (2005).

53.  A. Khan, “Ab initio studies on (H2O)14- clusters: existence of surface and interior-bound extra electrons”,  J. Chem. Phys. 125, 024307 (2006).

 54. A. Khan, “Reply to Comment on: Ab initio studies of (H2O)14-  clusters: Existence of surface and interior-bound extra electrons”, J.  Chem. Phys. 126, 027102 (2007).

55. 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).

56. A. Khan, “Reorganization and activation energies for hole transfer processes in DNA: a theoretical study”, J. Chem. Phys. 128, 075101 (2008).

57. 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).

58. 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).

59. 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).

60. 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).

61. 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)

62. V.T. Calabrese, J. W. Minns, A. Khan, “Suppression of α-Amylase inactivation in the presence of Ethanol: Application of a two-step model”, Biotechnology Progress 32, 1271-1275 (2016).