Robert Doyle

Laura J. and L. Douglas Meredith Professor Director of Graduate Studies Associate Chair - Department of Chemistry Syracuse University; Associate Professor of Medicine - SUNY, Upstate Medical University

Research Interests

Medicinal chemistry, bioconjugate chemistry, biochemistry

Professor Doyle's full CV can be found here.


  • B.A., 1998, Trinity College, Dublin, Ireland
  • Ph.D., 2002, Trinity College, Dublin, Ireland
  • Postdoctoral Fellow, 2002-2003, Australian National University
  • Postdoctoral Fellow, 2003-2005, Yale University
  • Joined Syracuse University Faculty, August 2005

Honors & Awards:

  • Laura J. and L. Douglas Meredith Professor 2016
  • Enterprise Ireland Fellowship, 1998
  • RSC Fellowship, 2002
  • Rudolph Anderson Foundation Fellowship, 2004
  • Ewing Marion Kauffman Foundation Award, 2008
  • ACS New Investigator Award, 2009
  • Tenure, February 2009
  • Faculty of 1000, Associate Member 2010
  • James K. Duah-Agyeman Award for Outstanding Faculty, 2011
  • Faculty Advisor of the Year, 2012
  • CNY College Educator of the Year, 2013
  • Promoted to Full Professor, 2014


  • CHE 103: Chemistry in the Modern World
  • CHE 106: General Chemistry
  • CHE 139: Honors General Chemistry
  • CHE 412/612: Metals in Medicine
  • CHE 422/622: Advanced Inorganic Laboratory
  • CHE 450: Independent Research
  • CHE 400/600: Chemical Biology
  • CHE 412/612: Metals in Biology & Medicine

Research Focus

Research in the Doyle group focuses on three main areas that join Inorganic chemistry and biology:
1. Utilizing vitamin B12 to deliver proteins orally or subcutaneously or to target metallo-probes/chemotherapeutics to tumor cells
2. Investigating energy independent metal-citrate transport in Gram positive bacteria
3. The coordination chemistry of metal-pyrophosphate complexes and the concomitant biological, magnetic and catalytic properties of such complexes.

While the three areas are seemingly quite disparate, the work actually encompasses a combined view of inorganic chemistry and biology and uses similar techniques that are the cornerstone of chemical and/or systems biology research. Each project is designed to educate students through challenging, applied research designed to answer current questions and needs such as: "How do bacteria acquire iron in a human host?", "Can we design an oral tetanus vaccine?" or "Can we prepare a defined VPO active catalyst at low temperature?". The research involves in-demand and cutting edge techniques from bioconjugate synthesis and in vivo protein expression and mutagenesis to radioflux assays and confocal microscopy. In addition, each student is responsible for all aspects of the project from design, through synthesis, purification, characterization, radiochemistry, in vitro assays (Enzyme inhibition, DNA binding/scission/unwinding, WSK, Ox-stress, apoptosis etc), to in vivo testing.

Work in our lab includes

1. Peptide/Protein Projects
Hypothesis: The vitamin B12 uptake pathway can be adopted to deliver clinically relevant doses of peptides/proteins .
 Mammals have a highly efficient uptake and transport mechanism in the gastrointestinal tract (GIT) for the absorption and cellular uptake of the vitamin B12 molecule (~1350 Da). The proposed delivery system would take advantage of this natural intrinsic factor (IF) mediated uptake mechanism to overcome the two major hurdles to peptide delivery, namely GIT proteolysis and transcytoses of the enterocyte [27]. Vitamin B12 first binds to haptocorrin, a salivary enzyme that can protect and transport B12 through the stomach and into the small intestine (see Figure 2). The B12 then binds to IF and proceeds down the small intestine where the complex binds to the IF receptor on the ileum wall. The IF-B12 receptor complex then undergoes endocytosis, releasing B12 into the blood serum where it is bound to transcobalamin II (TCII).

Doyle figure 13
Figure 1. Dietary uptake pathway for B12. Abbreviations: (HC) haptocorrin; (IF) intrinsic factor; (CB) cubilin receptor;
(MG) megalin; (TCII) transcobalamin II; (TCII-R) transcobalamin II receptor.

To adapt this uptake pathway for neuropeptide delivery, the recognition of, and affinity for, the various binding B12 proteins must not be lost or grossly diminished. Using insulin as the lead compound, we have previously synthesized and demonstrated, both in vitro and in vivo, the successful conjugation of a peptide hormone to B12. Conjugation to B12 then can both protect bound proteins from digestion and also facilitate their internalization and transport into blood serum overcoming the two major hurdles for oral peptide delivery mentioned earlier.

Shown here is a B12-insulin system that has greater in vivo glucose lowering ability than free insulin when administered orally [Susan Clardy, Dr. Timothy Fairchild (Murdoch University, Perth, Australia)].

Additional projects in this area include the development of new oral PYY and GLP systems (Chris Fazen).

Injections of peptide tyrosine tyrosine (PYY) have shown positive effects on appetite regulation. With nearly 400 million adults worldwide considered obese, these positive effects have sparked an increased interest in PYY research, including release profiles, receptor and subcutaneous targets, and medicinal applications. A major area of interest is oral delivery of PYY that can display clinically relevant outcomes related to weight loss in what would be a highly compliant, user-friendly route. The vitamin B12 (B12) dietary uptake pathway has already been successfully used for oral delivery of other peptides including erythropoietin and insulin (Doyle et al.), and it is hypothesized here that such a route could be used to orally and/or buccally deliver PYY.

In addition we are working on oral rotavirus and tetanus vaccines (Debbie Valentin, Josh Zylstra, Teresa Soldner and Soreen Cyphers)

Doyle Figure 3
Nerissa with her mammalian cells
(chinese hamster ovary cells)
Doyle Figure 7
Amy working with Tc in hot cell at
Nuclear Reactor, Hamilton, Ontario
Doyle Figure 9
Click image above to see tetanus toxoid
infected Placental cells (purple)
Doyle Figure 2
B12-Insulin conjugate coupled at B12 ribose –OH
goup and insulin BK29.
Doyle Figure 2d
B12-Insulin conjugate bound to B12
uptake protein TCII
(Insulin in red; B12 in yellow)

Doyle Figure 10
The tetanus toxoid light chain at 0 - 10 ns time
- steps from a 325K MD simulation
Doyle Figure 11
'Cobalt': Our 11 quad-core (44 total processors) cluster

1. Doyle, R. P., Kelly E. Henry, R. M. Burke, C. Elfers and C. L. Roth Vitamin B12 conjugation of Peptide-YY3-36 decreases food intake compared to native Peptide-YY3-36 upon subcutaneous administration in lean rats Endocrinology 2015, 156, 1739-1749.

2. Doyle, R. P., Ron. L. Bonaccorso, Oleg G. Chepurny, Christian Becker-Pauly, George G. Holz Enhanced peptide stability against protease degradation induced by Intrinsic factor binding of a vitamin B12 conjugate of exendin-4 Molecular Pharmaceutics 2015, accepted PMID: 26260673.

3. Doyle, R. P., Oluwatayo F. Ikotun, Bernadette V. Marquez, Christopher H. Fazen, Anna R. Kahkoska, Suzanne E. Lapi Investigating a vitamin B12 conjugate as a PET imaging probe ChemMedChem 2014, 9, 1244-1251.

4. Doyle, R. P., Susan Clardy-James, Oleg G. Chepurny, Colin A. Leech, George G. Holz, Synthesis, Characterization and Pharmacodynamics of Vitamin B12 Conjugated Glucagon-Like Peptide-1 ChemMedChem 2013, 8, 582-586. (selected as cover article)

5. Doyle, R. P., Susan Clardy-James, Jamie L. Bernstein Site selective oxidation of vitamin B12 using iodoxybenzoic acid Synlett 2012, 23, 2363-2366.

6. Doyle, R. P., Susan Clardy-James, Damian G. Allis, Timothy J. Fairchild, Examining the effects of vitamin B12 conjugation on the biological activity of insulin: A molecular dynamic and in vivo oral uptake investigation MedChemComm 2012, 3, 1054-1058. (Selected as cover article)

7. Doyle, R. P., Christopher Fazen, Debbie Valentin, Timothy J. Fairchild Oral Delivery of the Appetite Suppressing Peptide hPYY3-36 through the Vitamin B12 Uptake Pathway Journal of Medicinal Chemistry 2011, 54, 8707-8711.
8. Doyle, R. P., Anthony R. Vortherms, Anna Kahkoska, Amy E. Rabideau, Louise Lund Andersen, Mette Madsen A water soluble vitamin B12-Re(I) fluorescent conjugate for cell uptake screens: Use in the detection of cubilin in the lung cancer line A549 Chem. Commun., 2011, 47(35), 9792-9794.
9. Doyle, R. P.; Clardy, S. M.; Allis, D. G.; Fairchild, T. J. Vitamin B12 in Drug Delivery: Breaking through the barriers to a B12 bioconjugate pharmaceutical Expert Opinion on Drug Delivery, 2011, 8, 127-140

2. Energy Independent Metal-citrate transport in Gram Positive Bacteria

Important recent discoveries have been made that demonstrate Gram-positive bacteria can transport metal-citrate complexes in symport with one or two H+ per complex. While there has been extensive research conducted into citrate transport across membranes, there has been a dearth of research into secondary transporters that can transport metal-bound, complexed citrate. The CitMHS transporters investigated to date have the ability to selectively transport only certain metal-citrate complexes. Despite sharing amino acid sequence homology as high as 73%; predicting what complexes are transported remains difficult. Work by Cvitkovitch inStreptococcus mutans and our own studies in Streptomyces coelicolor showing selectivity for iron(III)-citrate transport, have led us to hypothesize the following:1,2

Streptomyces coelicolor A3(2) releasing actinorhodin (blue color).Courtesy of the John Innes Centre, Norwich, UK.

Iron(III)-citrate can by transported by a secondary transporter, allowing pathogenic bacteria access to a pool of iron in the form of iron-citrate, in human hosts, where iron-citrate can reach millimolar concentrations in blood serum. Selectivity for iron-citrate over other metal-citrate complexes and free citrate is achieved by a combination of complex stereochemistry, charge, nuclearity and transcription regulation. Such a series of surface exposed proteins may be critical for iron sequestration in pathogens and therefore would be prevalent as well as antigenic, making them antibody targets.

This work involves the study of metal transport and uptake proteins in Prokaryotic organisms, including the mechanistic and structural characterization of putative metal-citrate transporters from Streptomyces coelicolorKineococcus radiotolerans and Bacillus anthracis. We are systematically figuring out how these unusual proteins functions. While we know much of energy dependent metal-citrate transport (seeFecABCDE system), we know very little of energy independent metal-citrate transport. To do this, we have overexpressed and isolated pure protein in E. coli, begun mutagenesis studies and conducted extensive functional and kinetic studies in S. coelicolor and K. radiotolerans.

The long-term goal of this work is to understand the mechanism of metal-citrate complex selection, the fate of the complex upon uptake and the possible role these proteins may have in disease pathogenesis in bacteria such as B. anthracis. [Brian Huta, Qi Wen Li]

Figure 1. Model of the predicted membrane topology of CitSc.28 C-terminal region is predicted to be outside the membrane with the N-terminal region inside. Boxes indicate transmembrane helices. Residues being mutated are marked (orange for proton symport, blue for complex recognition/transport).

1. Doyle, R. P., Brian P. Huta and E. Robertson Metal-citrate complex transport in Kineococcus radiotolerans submitted Antonie van Leeuwenhoek 2015.

2. Doyle, R. P.; Brian Huta, Joshua J. Lensbouer, Adam J. Lowe, Jon Zubieta Metal-citrate complex uptake and CitMHS transporters- From coordination chemistry to possible vaccine development Inorg. Chim. Acta 2012, 125-134, 393. (Special issue ‘Metals in Medicine’)

3. Doyle, R. P.; Lensbouer, J. J. Secondary Transport of Metal-citrate Complexes: The CitMHS Family. Critical reviews in Molecular Biology and Biochemistry 2010, 45(5), 453–462.

4. Doyle, R. P.; Lensbouer, J. J.; Li, Q. W.; Estlinbaum, M. R161, K452 and R460 residues are vital for metal-citrate complex transport in the CitMHS secondary transport protein CitSc from Streptomyces coelicolor. Metallomics 2, 342-347, 2010.

5. Doyle, R. P.; Lensbouer, J. J.; Patel, A.; Sirianni, J. P. Functional Characterization and metal ion specificity of the Metal-Citrate complex transporter from Streptomyces coelicolor A3(2). J. Bacteriology, 190, 5616-5623, 2008.

3. Pyrophosphate Project

Hypothesis: Pyrophosphate coordination complexes can be readily synthesized and will produce organized molecular structures that show unique chemical and physical properties and reactivities. Such a series of pyrophosphate complexes will offer up low temperature oxidative catalysts, biological pro-drugs and unusual magnetic phenomena with broad impacts across chemistry, biology and materials science.

Inorganic pyrophosphate (PPi) is a diphosphate tetraanion ([O3P-O-PO3]4-) that is ubiquitous in nature. PPi plays a central role in a variety of bioenergetic processes, the -P-O-P- moiety acting, for instance, as the main chemical form in which energy is circulated in living cells. PPi has also been shown to be pivotal in the industrial catalytic conversion of butane to maleic anhydride and to mediate magnetic interactions between paramagnetic transition metal ions. We have demonstrated a 5-fold increase in magnetic coupling by controlled dehydration, ferromagnetism and spin canted magnetic phenomena. Biologically, we have shown these compounds can have picomolar cytotoxicity with a broad range of mechanisms of action (enzymatic, oxidative, DNA interaction) in cancer cells.

The long-term objective of our research program is to explore pyrophosphate as a ligand both from the fundamentals of the structures that can be produced and the functional properties (magnetic, biological, catalytic) that go hand in hand. This work is performed by Dr. Nadia Marino (PhD University of Calabria, Italy) and Graduate student Amanda Hoffman.


1. Doyle, R.P., Amanda E. Hoffman, Leann H. Miles, Carolyn Shoen, Michelle DeStefano and Michael Cynamon Clinical isolates of Candida albicans, Candida tropicalis, and Candida krusei have different susceptibilities to Co(II) and Cu(II) complexes, Biometals 2015, 28, 415-423.

2. Doyle, R. P.; Vortherms, A. R.; Marino, N.; Hoffman, A. E. Expanding Monomeric Pyrophosphate Complexes beyond Platinum. Inorg. Chem. 2010, 49, 6790–6792.

3. Doyle, R. P.; Ikotun, O. F.; Marino, N.; Kruger, P. E.; Julve, M. Exploring the coordination chemistry of Pyrophosphate, a Ligand of diverse Biological, Magnetic and Catalytic potential. Coord. Chem. Rev. 2010,254, 890-915.

4. Doyle, R. P.; Higbee, E. M.; Ouellette, W.; Ikotun, O. F. Pyrophosphate bridged complexes with picomolar cytotoxicity. J. Inorg. Biochem. 2009, 103, 1254-1264.

5. Doyle, R. P.; Ikotun, O. F.; Oullette, W.; Lloret, F.; Julve, M. Synthesis, Structural, Magnetic and Thermal Characterization of {[Cu(bipy)]2(µ-HP2O7)(µ-Cl)}•H2O. Eur. J. Inorg. Chem. 2008, 33, 5281-5286.

6. Doyle, R. P.; Marino, N.; Mastropietro, T. F.; Armentano, D.; De Munno, G.; Lloret, F.; Julve, M. Spin Canting in an Unprecedented Three-Dimensional Pyrophosphate- and 2,2'-Bipyrimidine-Bridged Cobalt(II) Framework. Dalton Trans. 2008, 38, 5152-5154.

Selected Publications

(SU Grads and/or Undergrads are underlined) (* is corresponding author)

  • Doyle, R. P., Nadia Marino, Susan K. Hanson, Peter Müller, Pyro without Fire: Synthesis, Structure and Reactivity of a dimeric Vanadyl-Pyrophosphate coordination complex Inorganic Chemistry 51, 10077-10079, 2012.
  • Doyle, R. P., Susan Clardy-James, Oleg G. Chepurny, Colin A. Leech, George G. Holz, Synthesis, Characterization and Pharmacodynamics of Vitamin B12 Conjugated Glucagon-Like Peptide-1 ChemMedChem 2013, 8, 582-586. (selected as cover article)
  • Doyle, R. P., Kelly E. Henry, Rebeca G. Balasingham, Anthony R. Vortherms, James A. Platts, John F. Valliant, Michael P. Coogan, Jon Zubieta, Emission wavelength variation with changes in excitation in a Re(I)/ bisthiazolate ligand complex that breaks the Kasha-Vavilov Rule Chem. Sci., 2013, 4, 2490-2496.
  • Doyle, R. P., Amanda E. Hoffman, Michelle DeStefano, Carolyn Shoen, Krishnamoorthy Gopinath, Digby F. Warner, Michael Cynamon Co(II) and Cu(II) Pyrophosphate complexes have selectivity and potency against Mycobacteria including multidrug-resistant M. tuberculosis Eur. J. Med. Chem., 70, 589-93, 2013.
  • Doyle, R. P., Oluwatayo F. Ikotun, Bernadette V. Marquez, Christopher H. Fazen, Anna R. Kahkoska, Suzanne E. Lapi Investigating a vitamin B12 conjugate as a PET imaging probe accepted ChemMedChem 2014.


Doyle pub

*Conjugate of Insulin and Vitamin B12 for Oral Delivery 1. US 2008-0242595 A1; 2. U.S. 2011-0092416A1
*Vitamin B12- Peptide Conjugate as Therapeutic Agent for Obesity US 2011-0092416 A1
*Functional Characterization and Metal Ion Specificity of the Metal-Citrate Complex Transporter from Steptomyces Coelicolor U.S. 2011-0189196A1
*Butanol Production Using Engineered Streptomyces Coelicolor US 2010-0255552A1
*Pyrophosphate Complexes and Methods of Treatment Using the Complexes U. S. 2011-0092465 A1