Research Accomplishments Research Accomplishments
A. Early Research and Translational Activities, 1976-1982. Dr. Serianni did his graduate studies in the Department of Biochemistry at Michigan State University, working under the guidance of Dr. Robert Barker. During this early part of his career, Dr. Serianni worked on the synthesis of stable isotopically labeled saccharides, mainly 13C, to be used in conjunction with NMR to probe their structures, dynamics and reactivities (chemical and enzymic) in solution. At this time (1976-1980), applications of labeled saccharides were largely undeveloped, in part because access to labeled saccharides was very limited. Dr. Serianni’s work addressed this need in three ways: (1) he developed a new and general chemical method to incorporate 13C and other stable isotopes into aldoses site-specifically by the process of cyanohydrin reduction (to be distinguished from the well-known but less efficient Kiliani-Fischer synthesis); (2) he demonstrated the use of enzymes as reagents to transform labeled aldoses prepared by cyanohydrin reduction into other valuable labeled carbohydrates such as ketoses (via aldose-ketose isomerases) and oligosaccharides (via sugar nucleotides and glycosyltransferases); and (3) he discovered a novel mechanism of saccharide backbone rearrangement (C1-C2 transposition), catalyzed by molybdate ion, that revolutionized the synthesis of labeled saccharides.
These key developments, especially (1) and (3), represented disruptive technologies that changed the field of saccharide isotopic labeling tremendously, and made possible new structure/function studies in chemistry, biochemistry and biomedicine. Testimony to their disruptive character is demonstrated by the fact that, in 1982, Dr. Serianni cofounded a company in the state of New York, Omicron Biochemicals Inc. (since then incorporated in the state of Indiana). This company addressed the rapidly expanding needs of researchers for labeled saccharides in chemical, biochemical, biomedical and clinical research. It is noteworthy that this translational activity occurred at a time when entrepreneurial activities were rare and often discouraged in academics (which contrasts markedly with present day sentiments). More than thirty years later, Omicron Biochemicals Inc. remains in operation, recently occupying (in 2006) a newly constructed 8000 sq. ft. research facility, and employing >10 BS-PhD-level scientists. The company’s web site lists > 600 labeled (and unlabeled) sugars prepared routinely on-site, and offers custom synthesis services for special applications. Omicron serves thousands of clients worldwide, and presently prepares materials ranging from reagent grade to cGMP-grade appropriate for human clinical trials. The impact of this entrepreneurial effort with respect to supporting and promoting scientific research in many diverse fields has been enormous. Dr. Serianni still serves as President and CEO of Omicron, and oversees the technical aspects of its operations and the development of new products and services.
B. Academic Career, 1982-1992. This period of Professor Serianni’s professional career focused mainly on the development of NMR methods to investigate the structures and reactivities of saccharides. Three main themes emerge from this body of work: (a) NMR-based kinetics measurements of saccharide anomerization; (b) the application of stable isotopes to investigate in vivo biological metabolism; and (c) the application of ab initio molecular orbital calculations to investigate saccharide structure and conformation.
Professor Serianni was the first to recognize that saturation–transfer NMR methods could be used to measure the unidirectional rate constants (as opposed to complex rate constants) of aldose anomerization in solution. The method hinges on the selective saturation of the acyclic carbonyl form of the aldose, or more specifically, the anomeric proton or carbon of the acyclic form, even though it comprises only a small percentage of the total forms (tautomers) present in solution (typically less than 1%). By measuring the rate of transfer of saturation to the cyclic forms (detected as a loss of signal intensity with increasing saturation time), first-order ring-opening rate constants for each cyclic form in solution can be measured. From the individual equilibrium constants also measured by NMR, ring-closing rate constants could be determined, thus fully defining these complex systems kinetically. The same methodology was applied to ketoses by limiting the experiment to carbon detection (e.g., C2 of fructose). The Serianni lab showed that furanose ring anomeric configuration controls the relative rates of ring-opening, with O1-O1 cis arrangements leading to enhanced ring-opening, presumably through an anchimeric assistance mechanism. In subsequent studies with phosphorylated sugars, his group showed the importance of intramolecular catalysis by phosphate in promoting anomerization, demonstrating that the magnitude of this catalysis is affected by ring configuration. These latter studies have important implications for biological metabolism when sugar phosphates are involved as metabolites; since many enzymes bind only one anomer, rates of anomerization can play a potential role in determining metabolic flux through some pathways (anomeric control).
C. Academic Career, 1993-present. The most recent period of research in the Serianni laboratory has focused mainly, but not exclusively, on the development of NMR spin-couplings as quantitative probes of saccharide structure and conformation in solution. This work was initiated in 1993 with the publication of a paper in JACS showing a Karplus-like relationship for 1JCC in saccharides; this study demonstrated the power of combining NMR studies with stable isotopes, and ab initio MO calculations, to investigate spin-coupling behaviors in these systems. This work was done in collaboration with Dr. Ian Carmichael of the Radiation Laboratory at Notre Dame. Since that time, the Serianni-Carmichael team has published over 50 papers on the characterization of NMR J-couplings in saccharides experimentally and theoretically (DFT), thereby extensively re-defining the importance and utility of carbon-based J-couplings (JCH and JCC) in saccharides. For example, in 1995, the Serianni-Carmichael team demonstrated the use of 1JCH values as conformational probes of furanose rings, and showed how these couplings respond to C-H bond orientational effects (pseudo-axial/pseudo-equatorial) and C-O bond rotations (vicinal lone-pair effects) in these ring systems. In 1998, this team published the first 3JCOCC Karplus curve relevant to the analysis of 3JCOCC values across O-glycosidic linkages. In this detailed work, they demonstrated the importance of terminal electronegative substituent effects on coupling magnitude and set the stage for quantitative interpretations of these couplings as a means of establishing linkage conformation in solution. In 2004, the Serianni group showed that J-couplings could be used to determine correlated conformations of exocyclic hydroxymethyl groups, since some of these couplings depend on two torsion angles. In 2005, 2JCCH values in saccharides were shown to depend heavily on C-O bond rotations involving the carbon bearing the coupled proton, leading to a new conformational constraint for O-glycosidic linkages. In 2006, Serianni’s group showed how 1JCH could be used to measure the strengths of H-bonds in aqueous solution, introducing the concept of “functional” J-couplings. In 2008, Serianni’s group demonstrated quantitatively the effect of internal electronegative substituents on 3JCOCC values, thus further defining the structural dependencies of these important NMR constraints. Most recently, the Serianni group has developed a new mathematical treatment of J-coupling ensembles (MA’AT) to calculate phi and psi populations in glycosidic linkages, thus providing experimentally based populations to validate MD predictions.
The Serianni group most recently has embarked on mechanistic studies of saccharide degradation using stable isotopes and NMR. Two studies are highlighted here. In 2011, they showed that the dicarbonyl sugar, 3-deoxyglucosone (3DG), degrades in aqueous solution via a 1,2-hydrogen transfer mechanism to give C2-epimeric metasaccharinic acids. This work follows up their prior work (Biochemistry, 2008) on the effect of pyridoxamine on 3DG degradation. These studies are relevant to diabetes mellitus, where high concentrations of glucose in blood and plasma result in the in vivo production of 3DG, which then inflicts cellular/tissue damage via protein glycation and other deleterious reactions. Very recently (2012), the Serianni group has discovered a novel rearrangement of the dicarbonyl sugar, D-glucosone, in which the molecule undergoes C1-C2 transposition during conversion to D-ribulose. This finding provides a second example of a reaction in saccharide chemistry in which C1-C2 transposition takes place (see molybdate reaction above).
Finally, in recent work performed in collaboration with Professor John Duman’s research group in the Department of Biological Sciences at Notre Dame, the Serianni team elucidated the structure of a novel non-protein thermal hysteresis compound built on a xylo-mannan oligosaccharide scaffold. This finding has recently been patented.