Temporomandibular Joint Ankylosis in Young Adult: A Case Report.

Temporomandibular joint (TMJ) ankylosis is a debilitating condition. It involves the mouth opening, dentofacial deformity, diet problem, and quality of life. When it occurs in a child, it can have devastating effects on the future growth and development of the jaws and teeth. Furthermore, in many cases it has a profoundly negative influence on the psychosocial development of the patient, because of the obvious facial deformity, which worsens with growth. TMJ ankylosis results in a limitation of the mouth opening. This disorder can result in an array of problems with diet, facial deformity, and poor oral hygiene. Three main surgical modalities described in the literature for its management are gap arthroplasty, interpositional arthroplasty and total joint replacement. Recurrence remains the main problem after surgery. Aggressive resection and intensive postoperative physiotherapy are recommended to prevent re-ankylosis.

Theoretical studies on the pyridoxal-5'-phosphate dependent enzyme dopa decarboxylase: Effect of Thr 246 residue on the co-factor-enzyme binding and reaction mechanism.

Decarboxylation of amino acid is a key step for biosynthesis of several important cellular metabolites in the biological systems. This process is catalyzed by amino acid decarboxylases and most of them use pyridoxal-5'-phosphate (PLP) as a co-factor. PLP is bound to the active site of the enzyme by various interactions with the neighboring amino acid residues. In the present investigation, density functional theory (DFT) and real-time dynamics studies on both ligand-free and ligand-bound dopa decarboxylases (DDC) have been carried out in order to elucidate the factors responsible for facile decarboxylation and also for proper binding of PLP in the active site of the enzyme. It has been found that in the crystal structure Asp271 interacts with the pyridine nitrogen atom of PLP through H-bonding in both native and substrate-bound DDC. On the contrary, Thr246 is in close proximity to the oxygen of 3-OH of PLP pyridine ring only in the substrate-bound DDC. In the ligand-free enzyme, the distance between the oxygen atom of 3-OH group of PLP pyridine ring and oxygen atom of Thr246 hydroxyl group is not favorable for hydrogen bonding. Thus, present study reveals that hydrogen bonding with O3 of PLP with a hydrogen bond donor residue provided by the enzyme plays an important role in the decarboxylation process.

Energy barriers and rates of tautomeric transitions in DNA bases: ab initio quantum chemical study.

Tautomeric transitions of DNA bases are proton transfer reactions, which are important in biology. These reactions are involved in spontaneous point mutations of the genetic material. In the present study, intrinsic reaction coordinates (IRC) analyses through ab initio quantum chemical calculations have been carried out for the individual DNA bases A, T, G, C and also A:T and G:C base pairs to estimate the kinetic and thermodynamic barriers using MP2/6-31G** method for tautomeric transitions. Relatively higher values of kinetic barriers (about 50-60 kcal/mol) have been observed for the single bases, indicating that tautomeric alterations of isolated single bases are quite unlikely. On the other hand, relatively lower values of the kinetic barriers (about 20-25 kcal/mol) for the DNA base pairs A:T and G:C clearly suggest that the tautomeric shifts are much more favorable in DNA base pairs than in isolated single bases. The unusual base pairing A':C, T':G, C':A or G':T in the daughter DNA molecule, resulting from a parent DNA molecule with tautomeric shifts, is found to be stable enough to result in a mutation. The transition rate constants for the single DNA bases in addition to the base pairs are also calculated by computing the free energy differences between the transition states and the reactants.