Identification of the lysine residue modified during the activation of acetimidylation of horse liver alcohol dehydrogenase.

A single amino group in horse liver alcohol dehydrogenase was modified with methyl(14C)acetimidate by a differential labeling procedure. Lysine residues outside the active site were modified with ethyl acetimidate while a lysine residue in the active site was protected by the formation of an enzyme-NAD+-pyrazole complex. After the protecting reagents were removed, the enzyme was treated with methyl(14C)acetimidate. Enzyme activity was enhanced 13-fold as 1.1 (14C)acetimidyl group was incorporated per active site. A labeled peptide was isolated from a tryptic-chymotryptic digest of the modified enzyme in 35% overall yield. Amino acid composition and sequential Edman degradations identified the peptide as residues 219-229; lysine residue 228 was modified with the radioactive acetimidyl group.     

Cytomegalovirus Infection in Children Undergoing Open-Heart Surgery

A group of 124 children undergoing open-heart surgery was followed prospectively in order to estimate the risk of cytomegalovirus (CMV) infection due to transfused blood.     

In vitro oxidative footprinting provides insight into apolipoprotein B‐100 structure in low‐density lipoprotein

Low‐density lipoprotein (LDL) is a major cholesterol carrier in human blood. Oxidations of apolipoprotein B‐100 (apo B‐100, LDL protein) could be proatherogenic and play critical roles in early stages of plaque formation in the arterial wall. The structure of apo B‐100 is still poorly understood, partially due to its size (550 KDa, 4563 amino acids). To gain an insight into LDL structure, we mapped the regions of apo B‐100 in human LDL that were prone to oxidation using peroxynitrite and hypochlorite as probes. In this study, LDL was incubated with various concentrations of peroxynitrite and sodium hypochlorite in bicarbonate buffer. The LDL protein apo B‐100 was delipidated, denatured, alkylated, and subjected to tryptic digestion. Tryptic peptides were analyzed employing LC‐MS/MS. Database search was performed against the apo B‐100 database (SwissProt accession #P04114) using “SEQUEST” algorithm to identify peroxynitrite and hypochlorite‐mediated oxidations markers nitrotyrosine, nitrotryptophan, hydroxy‐tryptophan, and 3‐chlorotyrosine. Several site‐specific oxidations were identified in apo B‐100 after treatment of intact LDL particles with the oxidants. We hypothesize that these regions could be accessible to oxidant and critical for early events in atherosclerotic plaque deposition.     

Phenotypic interactions between abscisic acid deficient tomato mutants

Summary A series of double mutant homozygotes have been produced from three wilty tomato mutants; flacca, sitiens and notabilis. The phenotypic interaction between the mutant genes has been studied. The severity of phenotype in the double mutants does not correspond to that predicted from the single mutant homozygotes. The results are discussed in relation to the probable involvement of the mutants in abscisic acid metabolism.     

Resolving UV Bioactinometric Results with Intensity and Time Distributions

A UV reactor with an annular design, a total liquid volume of 460[emsp4 ]ml, and outfitted with a single lamp with 1690[emsp4 ]mW of germicidal power was tested. Coliphage MS2 was used as a bioactinometer to measure the UV dose at a flow rate of 56.7[emsp4 ]ml/sec in water with a very low absorbance. The Beers Law coefficient was A₁₀0.003. The measured dose (MS2 bioactinometry) was 35.2±1.1[emsp4 ]mW-sec/cm².A retention time distribution was generated with a dye tracer study. The reactor was modeled as if flow was confined to ten equal volume paths existing as concentric rings around the lamp. The UV intensity along each path (ith intensity) was calculated to generate a simulated distribution of UV intensity in the reactor. The retention time distribution was subdivided to estimate the retention time associated with each decile jth time) of the total flow.Seven methods of associating the ith intensity with the jth retention time were used to produce simulated dose distributions for the reactor. The average UV dose for each distribution was calculated as the average of the products of I and t (AP protocol) and by the apparent survival (AS protocol), in which the predicted survival along each path was averaged to back-calculate dose from the reference batch inactivation curve. The average dose predicted assuming that time and intensity were independent was 51.5[emsp4 ]mW-sec/cm² based on the arithmetic average (AP protocol). Using the apparent survival method, the predicted dose for the independent distribution (I independent of t) was 36.4[emsp4 ]mW-sec/cm². Three methods of developing dependent structure between time and intensity were tested. In the best possible case for stratified flow (I negatively correlated with t) the calculated (AS) intensity was 46.3[emsp4 ]mW-sec/cm^2. In the worst case for stratified flow (I positively correlated with t) the AS intensity was 32.0[emsp4 ]mW-sec/cm². In a rational case where flows were assumed to be distributed parabolically (low flow at the wall and at the lamp) produced an AS intensity of 37.7[emsp4 ]mW-sec/cm². When either time or intensity was averaged, while the other variable was allowed to keep its distribution, the (AS) dose (time averaged 43.3[emsp4 ]mW-sec/cm², intensity averaged 41.0[emsp4 ]mW-sec/cm²), yielded a poor prediction compared to the measured value.The errors associated with averaging time, intensity, or both, far outweigh the errors associated with choosing a rational distribution or an independent distribution of time and intensity in the prediction. This observation is generally true whenever an organism is exposed to UV light in a flow through reactor such that the range of doses is within the portion of the inactivation curve exhibiting strong exponential decay.