Hongliang Xu's research interests lie in the interface of Mathematics and Biomedical Sciences. His expertise is in the areas of mathematical and computational crystallography, especially the development of novel mathematical models and optimal procedures for determining three-dimensional crystal structures from X-ray, neutron or powder diffraction data. The so-called “phase problem” in crystallography is the problem of determining the phase angles of the diffracted rays. The phase information, which is lost in the diffraction experiment, is in fact recoverable from the measurable intensities alone.
Xu is currently investigating novel procedures that combine the necessary complementary backgrounds from mathematical optimization and powder diffraction data from micro-crystalline samples. Specifically, he is developing mathematical optimization algorithms to solve the crystallographic phase problem in a reliable and efficient way. His work will lay the foundations of a new generation of crystallographic computing systems that will reveal structures important in the understanding of life, material science, and drug design.
Xu is a Graduate Faculty for the Applied and Computational Mathematics program at Buffalo State. He also serves as an adjunct Senior Research Scientist at the Hauptman-Woodward Medical Research Institute.
Journal Publication
Xu, H., Curry, J. and Narayanan, P. K. (2017). Using graph theory to rank college football teams. Journal of Sports Analytics (submitted).
Xu, H. (2017). Direct phasing of crystalline materials from X-ray powder diffraction, Lecture Notes in Computer Science, 165-175.
Xu, H. (2017). Constrained-induced direct phasing method, Acta Cryst. A73, 54-60.
Xu, H. (2016). Residual-based scattering factors, Acta Cryst. A72, 667-672.
Xu, H. (2010). Enhancing MAD FA data for substructure determination, Acta Cryst. D66, 945-949.
Xu, H., Smith, A.B., Sahinidis, N.V. & Weeks, C.M. (2008). SnB version 2.3: triplet sieve phasing for centrosymmetric structures, J. Appl. Cryst. , 41, 644-646.
Xu, H. & Weeks, C.M. (2008). Rapid and automated substructure solution by Shake-and-Bake, Acta Cryst. D64, 172-177.
Smith, A.B., Xu, H. & Sahinidis, N.V. (2007). An integer minimal principle and triplet sieve method for phasing centrosymmetric structures, Acta Cryst. A63, 164-171.
Xu, H. & Hauptman, H.A. (2006). Recent advances in direct phasing methods for heavy-atom substructure determination, Acta Cryst. D62, 897-900.
Hauptman, H.A., Langs, D.A. & Xu, H. (2005). The phase problem in neutron crystallography, p.187-194. Hydrogen- and Hydration-Sensitive Structural Biology, KubaPro Co., Ltd., Tokyo, Japan.
Xu, H., Hauptman, H.A. & Langs, D.A. (2005). Novel statistical approach to the phase problem in neutron crystallography, p.197-205. Hydrogen- and Hydration-Sensitive Structural Biology, KubaPro Co., Ltd., Tokyo, Japan.
Langs, D.A., Hauptman, H.A. & Xu, H. (2005). Future prospects for the phase determination of macromolecular structures from neutron data alone, p.207-212. Hydrogen- and Hydration-Sensitive Structural Biology, KubaPro Co., Ltd., Tokyo, Japan.
Xu, H. & Hauptman, H.A. (2004). Statistical approach to the phase problem. Acta Cryst. A60, 153-157.
Xu, H. & Hauptman, H.A. (2003). On integrating the techniques of direct methods and SIRAS: the probabilistic theory of doublets and its applications. Acta Cryst. A59, 60-65.
Weeks, C.M., Blessing, R.H., Miller, R., Mungee, R., Potter, S.A., Rappleye, J., Smith, G.D., Xu, H. & Furey W. (2002). Towards automated protein structure determination: BnP, the SnB-PHASES interface. Z. Kristallogr. 217, 686-693.
Hauptman, H.A., Guo, D.Y., Xu, H. & Blessing, R.H. (2002). Algebraic direct methods for few-atoms structure models. Acta Cryst. A58, 361-369.
Xu, H., Hauptman, H.A. & Weeks, M. (2002). Sine-enhanced Shake-and-Bake: the theoretical basis and applications to se-atom substructures. Acta Cryst. D58, 90-96.
Xu, H. & Hauptman, H.A. (2000). On the extrapolation of the magnitudes |E| of the normalized structure factors E. Acta Cryst. A56, 284-287.
Weeks, C.M., Xu, H., Hauptman, H.A. & Shen, Q. (2000). Shake-and-Bake applications using simulated refernce-beam data for crambin. Acta Cryst. A56, 280-283.
Xu, H., Weeks, C.M., Deacon, A., Miller, R. & Hauptman, H.A. (2000). Ill-conditioned Shake-and-Bake: the trap of the false minimum. Acta Cryst. A56, 112-118.
Xu, H., Hauptman, H.A., Weeks, C.M. & Miller, R. (2000). P1 Shake-and-Bake: can success be guaranteed? Acta Cryst. D56, 238-240.
Hauptman, H.A., Xu, H., Weeks, C.M. & Miller, R. (1999). Exponential Shake-and-Bake: theoretical basis and applications. Acta Cryst. A55, 891-900.
Xu, H. (1998). Precise solution of wave equation. Ph.D. Dissertation. University at Buffalo, State University of New York.
Conference Presentation (Oral)
Xu, H. Shake-and-Bake method for Structure Determination. 3rd International Symposium on Biomathematics and Ecology: Education and Research. Normal, IL, 2010.
Xu, H., Weeks, C. M. & Blessing, R. H. Extending the power of PowSnB. American Crystallographic Association Annual Meeting. Chicago, IL, 2010.
Xu, H., Weeks, C. M. & Blessing, R. H. Powder Shake-and-Bake method. 11th European Powder Diffraction Conference, Warsaw, Poland. September, 2008.
Xu, H., Weeks, C. M., Some effects of experimental error on substructure determination. American Crystallographic Association Annual Meeting. Knoxville, TN, May 2008.
Langs, D. A., Xu, H. & Hauptman, H. A. Buffalo group HFSP progress report. HFSP Symposium on Direct Methods in Macromolecular Neutron Diffraction, Hitachi, Japan. August 2008.
Xu, H. & Hauptman, H. A. Shake-and-Bake algorithm for structure determination. SIAM conference on Mathematical Aspects of Material Science. Philadelphia, PA, May 2008.
Xu, H. Direct methods of X-ray crystallography. Special Colloquium in Applied Mathematics, Buffalo State College, Buffalo, NY October 2007.
Langs, D.A., Xu, H. & Hauptman, H.A. Direct methods phase determination of unresolved neutron SIR D/H substructures. HFSP Symposium on Direct Methods in Macromolecular Neutron Diffraction, Grenoble, France, October 2007.
Xu, H, Langs, D.A. & Hauptman, H.A. Recent advances in neutron phase problem. International workshop on Ibaraki Biological Crystal Diffractometer (BIX Type). Hitachi, Japan. March 2007.
Xu, H. Direct methods of crystallographic phase problem. Seminar at Ibaraki University, Ibaraki, Japan. March 2007.
Hauptman, H.A., Langs, D.A. & Xu, H. Direct methods in neutron crystallography. HFSP Symposium on Direct Methods in Macromolecular Neutron Diffraction, Buffalo, NY, October 2006.
Langs, D.A., Xu, H & Hauptman, H.A. A working outline for neutron D/H SIR phase determination. HFSP Symposium on Direct Methods in Macromolecular Neutron Diffraction, Buffalo, NY, October 2006.
Weeks, Potter, Shah, Xu, Green, Miller, Pasupulati & Furey. Adapting BnP for different computing environments. ACA Annual Meeting, Hawaii, HL, July 2006.
Hauptman, H.A., Langs, D.A. & Xu, H. New possibilities for the determination of macromolecular structures from selected H/D derivative crystals utilizing neutron data alone. ACA Annual Meeting, Hawaii, HL, July 2006.
Xu, H., Weeks, C.M., and Hauptman, H.A., Recent Advances in Direct Phasing Methods for Protein Structure Determination, International Workshop on Recent Advances in Phasing Methods for High-Throughput Protein Structure Determination, Peking University, Beijing, China, October 2005.
Xu, H., Weeks, C.M., and Hauptman, H.A., Statistical Direct Methods of Phase Determination. XXth Congress and General Assembly of the International Union of Crystallography, Florence, Italy, August 2005.
Furey, Pasupulati, Potter, Xu, Miller, and Weeks, Automated Protein Structure Determination with BnP, XXth IUCr Congress and General Assembly, Florence, Italy, August 2005.
Hauptman, H.A, and Xu, H., The Phase Problem of Crystallography, Workshop on Developing a Program in Computational Science, Buffalo State College, Buffalo, NY, March 2005.
Langs, D.A., Hauptman, H.A., and Xu, H., Can Macromolecular Structure be Determined from Neutron Data Alone? ORCS2005 Satellite Meeting, Tokai, Japan, January 2005.
Xu, H., Hauptman, H.A., and Langs, D.A., Recent Advances in Phasing Methods for Neutron Structure Determination, ORCS2005 Satellite Meeting, Tokai, Japan, January 2005.
Hauptman, H.A., Langs, D.A., and Xu, H., The Neutron Crystallographic Phase Problem, ORCS2005 Satellite Meeting, Tokai, Japan, January 2005.
Langs, D.A., Hauptman, H.A., and Xu, H., Future Prospects for the Phase Determination of Macromolecular Structures from Neutron Data Alone. ORCS Summary International Workshop, Tokyo, Japan, January 2005.
Hauptman, H.A., Langs, D.A., and Xu, H., The Phase Problem in Neutron Crystallography, ORCS Summary International Workshop, Tokyo, Japan, January 2005.
Xu, H., Hauptman, H.A., and Langs, D.A., Novel Statistical Approach to the Phase Problem in Neutron Crystallography, ORCS Summary International Workshop, Tokyo, Japan, January 2005.
Xu, H., Statistical Approach to the Phase Problem of X-Ray Crystallography, 2004 CHESS Users’ Meeting, Cornell University, Ithaca, NY, June 2004.
Xu, H., Novel Algorithms for Crystallographic Computing, Workshop on New Research Directions in Macromolecular Structure Determination, Cornell University, Ithaca, NY, June 2004.
Xu, H., The Probabilistic Theory of the Structure Invariants, Mathematics/Crystallography seminar at the Department of Mathematics, SUNY at Buffalo, April 2002.
Hauptman, H.A., Xu, H., and Weeks, C.M., Recent Advances in the Direct Methods of X-ray Crystallography, Special Symposium: The Role of Protein Structure Prediction in the Post-Genomic Era, Cornell University, Ithaca, NY, October 2001.
Xu, H., The applications of SnB, Workshop at Global Research and Development, Pfizer Inc., Ann Arbor, MI, May 2001.
Xu, H., Hauptman, H.A., and Weeks, C.M., Enantiomorph Specific Shake-and-Bake, 58th Pittsburgh Diffraction Conference, Pittsburgh, PA, October 2000.
Conference Presentation (Poster)
Xu, H. Extending the powder of PowSnB. 11th Annual Faculty/Staff Research and Creativity Fall Forum, Buffalo State College, Buffalo, NY, October, 2010.
Langs, D. A., Xu, H. & Hauptman, H. A. Prospectives for macromolecular structure determination via neutron isomorphous replacement data. American Crystallographic Association Meeting, Knoxville, TN, May 2008.
Langs, D.A., Xu, H & Hauptman, H.A. Determination of detailed envelopes of SIR D/H amino acid substructures at less than inter-atomic resolution. American Crystallographic Association Meeting, Salt Lake City, UT, August 2007.
Xu, H, Weeks, C.M. & Hauptman, H.A. Rapid and automated substructure determination. American Crystallographic Association Meeting, Hawaii, HL, July 2006.
Langs, D.A., Hauptman, H.A., and Xu, H., Neutron Structure Determination via Macromolecular H/D Derivatives, XXth IUCr Congress and General Assembly, Florence, Italy, August 2005.
Langs, D.A., Xu, H., and Hauptman, H.A., Neutron Phasing Methods Applicable to D/H SIR Replacement Derivatives, Conference on New Frontiers in Neutron Macromolecular Crystallography, Oak Ridge National Lab, Oak Ridge, TN, July 2005.
Furey, Pasupulati, Potter, Xu, Miller, and Weeks, Recent Developments in the BnP Package for Automated Protein Structure Determination, American Crystallographic Association Meeting, Orlando, FL, May 2005.
Hauptman, H.A., Langs, D.A., and Xu, H., Combining Neutron Diffraction with Isomorphous Replacement. American Crystallographic Association Meeting, Orlando, FL, May 2005.
Xu, H., Weeks, C.M., Hauptman, H.A., and Langs, D.A., A Recent Advance in the Direct Methods of Phase Determination, American Crystallographic Association Meeting, Orlando, FL, May 2005.
Weeks, Potter, Xu, Miller, Pasupulati & Furey, Automated Applications of BnP. II. Test Results. American Crystallographic Association Meeting, Chicago, IL, July 2004.
Furey, Pasupulati, Potter, Xu, Miller & Weeks, Automated Applications of BnP. I. Methodology. American Crystallographic Association Meeting, Chicago, IL, July 2004.
Xu, H. and Hauptman, H.A., Novel Statistical Approach to the Phase Problem. American Crystallographic Association Meeting, Chicago, IL, July 2004.
Xu H., Quasi-MAD Phasing, American Crystallographic Association Meeting, Covington, KY, July 2003.
Weeks, C.M., Blessing, R.H., Miller, R., Mungee, R., Potter, S.A., Rappleye, J., Smith, G.D., Xu, H., and Furey, W., Integrating Direct Methods into a Semi-Automated, Protein-Phasing Package, XIXth IUCr Congress and General Assembly, Geneva, Switzerland, August 2002.
Xu, H. and Hauptman, H.A., On Integrating the Techniques of Direct Methods and SIRAS. II. The Initial Applications, XIXth IUCr Congress and General Assembly, Geneva, Switzerland, August 2002.
Hauptman, H.A. and Xu, H., On Integrating the Techniques of Direct Methods and SIRAS. I. The Theoretical Basis, XIXth IUCr Congress and General Assembly, Geneva, Switzerland, August 2002.
Xu, H. and Hauptman, H.A., On Integrating the Techniques of Direct Methods and SIRAS. The Theoretical Basis and Applications, American Crystallographic Association Annual Meeting, San Antonio, TX, May 2002.
Weeks, C.M., Rappleye, J., Furey, W., Miller, R., Potter, S.A., Smith, G.D. and Xu, H., BnP: The SnB-PHASES Interface, American Crystallographic Association Meeting, Los Angeles, CA, July 2001.
Xu, H., Weeks, C. M. and Hauptman, H. A., Sine-Enhanced Shake-and-Bake. II. Initial Applications, American Crystallographic Association Meeting, Los Angeles, CA, July 2001.
Hauptman, H.A., Xu, H., and Weeks, C.M., Sine-Enhanced Shake-and-Bake. I. Theoretical Basis, American Crystallographic Association Meeting, Los Angeles, CA, July 2001.
Hauptman, H. and Xu, H., The Probabilistic Theory of the Structure Invariants Assuming a Substructure to be Known, XIXth European Crystallographic Meeting, Nancy, France, August 2000.
Xu, H. and Hauptman, H. A., On Integrating the Techniques of Direct Methods with SIRAS, American Crystallographic Association Meeting, St. Paul, MN, July 2000.
Hauptman, H.A., Xu, H., Weeks, C.M., and Miller, R., Is 100% Success for Shake-and-Bake Possible? 57th Pittsburgh Diffraction Conference, Columbus, OH, October 1999.
Hauptman, H.A., Weeks, C.M., Xu, H., and Shen, Q., Combining Shake-and-Bake with Multiple Beam Diffraction Data: A Simulation? XVIII IUCr Congress and General Assembly, Glasgow, Scotland, August 1999.
Xu, H., Hauptman, H.A., Weeks, C.M., and Miller, R., Exponential Shake-and-Bake: Can Success Be Guaranteed? XVIII IUCr Congress and General Assembly, Glasgow, Scotland, August 1999.
Hauptman, H.A, Xu, H., Weeks, C.M., and Miller, R., Is 100% Success for Shake-and-Bake Possible? American Crystallographic Association Meeting, Buffalo, NY, May 1999.
Weeks, C.M., Xu, H., Hauptman, H.A., and Shen, Q., Shake-and-Bake Applications Using Simulated Multiple-Beam and Reference-Beam Data, American Crystallographic Association Meeting, Buffalo, NY, May 1999.
Weeks, C.M., Xu, H., Miller, R., and Hauptman, H.A., Shake-and-Bake Summer ’98 Update: Improving Limited Data with Magnitude Estimation. 18th European Crystallographic Meeting, Praha, Czech Republic, August 1998.
Xu, H., Weeks, C.M., Miller, R., and Hauptman, H.A., Applications of an Exponential Minimal Function, American Crystallographic Association Meeting, Arlington, VA, July 1998.
