This chapter provides an overview of recent progress in understanding proton transfer in RNA enzymes. It was over 10 years ago that the previous book by the same editors was published. In that volume, there was no chapter on proton transfer. Indeed, it was unclear whether proton transfer made important contributions to RNA catalysis. Many things have changed in the last decade. Most importantly...

Group transfer reactions catalyzed by enzymes have assumed a position of intense interest in contemporary enzymology (1). Well known examples of radicals capable of being transferred in such reactions are methyl, glycosyl, aeetyl, phosphoryl, pept,idyl, nucleosidyl, and nucleotidyl, in addition to the transport of hydrogen as seen with the familiar nuoleot.ide coenzymes. In this paper we wish t...

A role for protein dynamics in enzymatic catalysis of hydrogen transfer has received substantial scientific support, but the connections between protein structure and catalysis remain to be established. Valine residues 203 and 207 are at the binding site for the nicotinamide ring of the coenzyme in liver alcohol dehydrogenase and have been suggested to facilitate catalysis with "protein-promoti...

The discovery of RNA catalysis provided a paradigm shift in biology, insight into the evolution of life on the planet and a challenge to understand its mechanistic origins. RNA has limited catalytic resources that must be used to maximal effect. Consequently, RNA catalysis tends to be multifactorial, with several processes contributing to an overall significant enhancement of reaction rate. The...

Sodium borohydride (NaBH4) hydrogen storage systems offer many advantages for hydrogen storage applications. The physical processes nside a NaBH4 packed bed reactor involve multi-component and multi-phase flow and multi-mode heat and mass transfer. These processes are lso coupled with reaction kinetics. To guide reactor design and optimization, a reactor model involving all of these processes i...

background: there is no doubt that luteal phase support is essential to enhance the reproductive outcome in ivf cycles. in addition to progesterone and human chorionic gonadotropin, several studies have described gnrh agonists as luteal phase support to improve implantation rate, pregnancy rate and live birth rate, whereas other studies showed dissimilar conclusions. all of these studies have b...

Sodium borohydride (NaBH4) hydrogen storage systems offer many advantages for hydrogen storage applications. The physical processes inside a NaBH4 packed bed reactor involve multi-component and multi-phase flow and multi-mode heat and mass transfer. These processes are also coupled with reaction kinetics. To guide reactor design and optimization, a reactor model involving all of these processes...

in this paper, the problem of turbulent forced convection flow of water- alumina nanofluid in a uniformly heated pipe has been thoroughly investigated. in numerical study, single and two-phase models have been used. in single-phase modeling of nanofluid, thermal and flow properties of nanofluid have been considered to be dependent on temperature and volume fraction. effects of volume fraction a...

heat transfer phenomena in batch fluidized bed dryer have been studied and analyzed using three phase model including solid phase, interstitial gas phase and bubble phase based on rizzi model. new correlations of heat transfer coefficient to surrounding and convection heat transfer coefficient between solid and interstitial gas are being proposed. in addition, some modifications have been done ...