Signal-difference-to-noise comparison of temporal subtraction, kV-switching dual-energy and photon-counting dual-energy x-ray angiography.

Background: Dual-energy (DE) x-ray angiography with photon-counting detectors (PCDs) may enable single-exposure DE imaging of coronary vasculature.

Purpose: To compare the iodine signal-difference-to-noise ratio (SDNR) of single-exposure DE angiography with digital subtraction angiography (DSA) and kV-switching DE angiography for matched patient x-ray exposure.

Methods: In a phantom study, we determined the technique parameters that maximized the iodine SDNR per root entrance air kerma for DSA, kV-switching DE angiography and single-exposure DE angiography.

Experimental optimization of single-exposure dual-energy angiography with photon-counting x-ray detectors.

Background: Photon-counting x-ray detectors may enable single-exposure dual-energy (DE) x-ray angiography.

Purpose: The purpose of this paper is to experimentally optimize the energy thresholds and tube voltage for single-exposure DE x-ray angiography.

Methods: We optimized single-exposure DE x-ray angiography using the iodine signal-difference-to-noise ratio (SDNR) per root patient air kerma (κ) as a figure of merit.

Theoretical comparison of energy-resolved and digital-subtraction angiography.

Background: X-ray coronary angiography is a sub-optimal vascular imaging technique because it cannot suppress un-enhanced anatomy that may obscure the visualization of coronary artery disease.

Purpose: The purpose of this paper is to evaluate the theoretical image quality of energy-resolved x-ray angiography (ERA) implemented with spectroscopic x-ray detectors (SXDs), which may overcome limitations of x-ray coronary angiography.

Methods: We modeled the large-area signal-difference-to-noise (SDNR) of contrast-enhanced vasculature in ERA images and compared with that of digital-subtraction angiography (DSA), which served as a gold standard vascular imaging technique.

Using bispecific antibodies in forced degradation studies to analyze the structure-function relationships of symmetrically and asymmetrically modified antibodies.

Forced degradation experiments of monoclonal antibodies (mAbs) aid in the identification of critical quality attributes (CQAs) by studying the impact of post-translational modifications (PTMs), such as oxidation, deamidation, glycation, and isomerization, on biological functions. Structure-function characterization of mAbs can be used to identify the PTM CQAs and develop appropriate analytical and process controls. However, the interpretation of forced degradation results can be complicated because samples may contain mixtures of asymmetrically and symmetrically modified mAbs with one or two modified chains.

A genomewide screen for suppressors of Alu-mediated rearrangements reveals a role for PIF1.

Alu-mediated rearrangement of tumor suppressor genes occurs frequently during carcinogenesis. In breast cancer, this mechanism contributes to loss of the wild-type BRCA1 allele in inherited disease and to loss of heterozygosity in sporadic cancer. To identify genes required for suppression of Alu-mediated recombination we performed a genomewide screen of a collection of 4672 yeast gene deletion mutants using a direct repeat recombination assay.

The Schizosaccharomyces pombe Pfh1p DNA helicase is essential for the maintenance of nuclear and mitochondrial DNA.

Schizosaccharomyces pombe Pfh1p is an essential member of the Pif family of 5'-3' DNA helicases. The two Saccharomyces cerevisiae homologs, Pif1p and Rrm3p, function in nuclear DNA replication, telomere length regulation, and mitochondrial genome integrity. We demonstrate here the existence of multiple Pfh1p isoforms that localized to either nuclei or mitochondria.

Enzymatic resolution of chiral phosphinate esters.

The bacterial phosphotriesterase has been shown to catalyze the stereoselective hydrolysis of phosphinate esters. The wild-type enzyme preferentially hydrolyzes the SP-enantiomers of methyl phenyl p-X-phenylphosphinate esters by 3 orders of magnitude. The mutant enzyme, I106T/F132A/H254G/H257W, exhibits the opposite stereoselectivity and hydrolyzes the RP-enantiomer up to 30 times faster than the corresponding SP-enantiomer.

Mechanism for the hydrolysis of organophosphates by the bacterial phosphotriesterase.

Phosphotriesterase (PTE) from Pseudomonas diminuta is a zinc metalloenzyme that hydrolyzes a variety of organophosphorus compounds. The kinetic parameters of Zn/Zn PTE, Cd/Cd PTE, and a mixed-metal Zn/Cd hybrid PTE were obtained with a variety of substrates to determine the role of each metal ion in binding and catalysis. pH-rate profiles for the hydrolysis of diethyl p-nitrophenyl phosphate (I) and diethyl p-chlorophenyl phosphate (II) demonstrated that the ionization of a single group in the pH range of 5-10 was critical for substrate turnover.

Operational control of stereoselectivity during the enzymatic hydrolysis of racemic organophosphorus compounds.

The wild-type bacterial phosphotriesterase catalyzes the stereoselective hydrolysis of racemic pairs of organophosphorus compounds. The enzymatic stereoselectivity can be substantially enhanced via systematic alteration of the pKa for the leaving group phenol in the target substrates. These changes alter the rate-limiting step for substrate turnover from a diffusional event to phosphorus-oxygen bond cleavage.