Kinetic studies of the active sites functioning in the quinohemoprotein fructose dehydrogenase

AbstractSteady-state kinetic analysis was performed on the reaction between d-fructose and ferricyanide with the quinohemoprotein fructose dehydrogenase from Gluconobacter species. The d-fructose oxidation dependence on the ferricyanide concentration resulted in a series of parallel reciprocal plots, and the reaction was assumed to proceed by a ping-pong type of mechanism. A reciprocal plot of the reduction of ferricyanide at saturating concentration of d-fructose gave a break which was considered to appear as a result of the two active centers, namely PQQ and heme e functioning. A scheme of action is proposed and the bimolecular rate constant of the d-fructose oxidation, the kcat for PQQ and the electron transfer rate between the PQQH2 and heme c are calculated and account for 2.2 ± 0.4.104 M−1s−1, (93 ± 14) and (162 ± 7) s−1, respectively

Small Molecule Immunosensing Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) biosensors utilize refractive index changes to sensitively detect mass changes at noble metal sensor surface interfaces. As such, they have been extensively applied to immunoassays of large molecules, where their high mass and use of sandwich immunoassay formats can result in excellent sensitivity. Small molecule immunosensing using SPR is more challenging. It requires antibodies or high-mass or noble metal labels to provide the required signal for ultrasensitive assays. Also, it can suffer from steric hindrance between the small antigen and large antibodies. However, new studies are increasingly meeting these and other challenges to offer highly sensitive small molecule immunosensor technologies through careful consideration of sensor interface design and signal enhancement. This review examines the application of SPR transduction technologies to small molecule immunoassays directed to different classes of small molecule antigens, including the steroid hormones, toxins, drugs and explosives residues. Also considered are the matrix effects resulting from measurement in chemically complex samples, the construction of stable sensor surfaces and the development of multiplexed assays capable of detecting several compounds at once. Assay design approaches are discussed and related to the sensitivities obtained

The Founder’s Lecture 2009: advances in imaging of osteoporosis and osteoarthritis

The objective of this review article is to provide an update on new developments in imaging of osteoporosis and osteoarthritis over the past three decades. A literature review is presented that summarizes the highlights in the development of bone mineral density measurements, bone structure imaging, and vertebral fracture assessment in osteoporosis as well as MR-based semiquantitative assessment of osteoarthritis and quantitative cartilage matrix imaging. This review focuses on techniques that have impacted patient management and therapeutic decision making or that potentially will affect patient care in the near future. Results of pertinent studies are presented and used for illustration. In summary, novel developments have significantly impacted imaging of osteoporosis and osteoarthritis over the past three decades

Pharmacokinetic-Pharmacodynamic Modeling in Pediatric Drug Development, and the Importance of Standardized Scaling of Clearance.

Pharmacokinetic/pharmacodynamic (PKPD) modeling is important in the design and conduct of clinical pharmacology research in children. During drug development, PKPD modeling and simulation should underpin rational trial design and facilitate extrapolation to investigate efficacy and safety. The application of PKPD modeling to optimize dosing recommendations and therapeutic drug monitoring is also increasing, and PKPD model-based dose individualization will become a core feature of personalized medicine. Following extensive progress on pediatric PK modeling, a greater emphasis now needs to be placed on PD modeling to understand age-related changes in drug effects. This paper discusses the principles of PKPD modeling in the context of pediatric drug development, summarizing how important PK parameters, such as clearance (CL), are scaled with size and age, and highlights a standardized method for CL scaling in children. One standard scaling method would facilitate comparison of PK parameters across multiple studies, thus increasing the utility of existing PK models and facilitating optimal design of new studies

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Solute transfer in on-line analytical flow-through dialyzers

Mass transfer in infinite parallel-plate dialyzers with co-flow between sample and detector streams is discussed for three different theoretical models. Analytical solutions with coupled diffusion and membrane transfer equations were obtained for plug flow in both channels. The finite-difference approximation method was used to obtain numerical solutions for a laminar-flow regime. Results obtained with a mixing-cup model under steady-state conditions were also included. With the dimensions typical for analytical dialyzers, there were only small differences between the laminar-flow and plug-flow models. The mixing-cup model predicted higher fluxes through the membrane than the other two models, particularly when the channel heights were increased. The theoretical results were compared with experimental results for dialysis of zinc(II) ions and the flow dependence agreed reasonably well with theory provided that the hydrostatic pressures were equal on both sides, and that stresses which could result in membrane bulging were kept low.Download full text in PD

Flow injection determinations of glucose and adenosine-5'¬-triphosphate (ATP) based on a packed-bed glucokinase reactor

Bull. Chem. Soc. Ethiop. 1994, 8(2), 51-60