Field and laboratory emission cell automation and control system for investigating surface chemistry reactions

A novel system [field and laboratory emission cell (FLEC) automation and control system] has been developed to deliver ozone to a surface utilizing the FLEC to simulate indoor surface chemistry. Ozone, humidity, and air flow rate to the surface were continuously monitored using an ultraviolet ozone monitor, humidity, and flow sensors. Data from these sensors were used as feedback for system control to maintain predetermined experimental parameters. The system was used to investigate the chemistry of ozone with alpha-terpineol on a vinyl surface over 72 h. Keeping all other experimental parameters the same, volatile organic compound emissions from the vinyl tile with alpha-terpineol were collected from both zero and 100 ppb (parts per 10(9)) ozone exposures. System stability profiles collected from sensor data indicated experimental parameters were maintained to within a few percent of initial settings. Ozone data from eight experiments at 100 ppb (over 339 h) provided a pooled standard deviation of 1.65 ppb and a 95% tolerance of 3.3 ppb. Humidity data from 17 experiments at 50% relative humidity (over 664 h) provided a pooled standard deviation of 1.38% and a 95% tolerance of 2.77%. Data of the flow rate of air flowing through the FLEC from 14 experiments at 300 ml/min (over 548 h) provided a pooled standard deviation of 3.02 ml/min and a 95% tolerance range of 6.03 ml/min. Initial experimental results yielded long term emissions of ozone/alpha-terpineol reaction products, suggesting that surface chemistry could play an important role in indoor environments.

Use of solid-phase microextraction to detect and quantify gas-phase dicarbonyls in indoor environments

Solid-phase microextraction (SPME) was evaluated for the detection and quantification of the gas-phase dicarbonyls, glyoxal (GLY) and methylglyoxal (MGLY). Additionally, polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), and carbowax/divinylbenzene (CW/DVB) fibers were tested to determine the optimum fiber for detection of these species. GLY and MGLY were derivatized with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA), extracted with SPME from headspace or bag chamber and then analyzed by GC/MS. The PDMS/DVB SPME fiber for on-fiber derivatization and subsequent sampling for gas-phase methylglyoxal provided the optimum combination of analytical reproducibility and sensitivity. Linearity of the calibration curve was achieved across a range of 11-222 microg/m(3) (4-75 ppb).

Purification and properties of a proteolytic enzyme from French beans

1. A proteolytic enzyme with some features of a carboxypeptidase has been purified some 1180-fold from the sap of French beans (Phaseolus vulgaris var. Prince). A bright blue protein, plastocyanin, was separated from the enzyme by DEAE-cellulose chromatography. 2. Unlike carboxypeptidase A or B of animal origin, there is no evidence that the enzyme is a metalloprotein. There was no stimulation of activity by a number of metal ions, reducing agents or 2-mercapto-ethanol. Neither EDTA nor 1,10-o-phenanthroline inhibited the enzyme. 3. The proteolytic enzyme from beans, readily soluble at neutral or slightly acidic pH values, has a pH optimum of pH5.6 for the hydrolysis of leucine from benzyloxy-carbonylglycyl-l-leucine. Solutions of the enzyme in 0.1m-sodium acetate, pH5.5, lose about 2% of their activity/week at 4 degrees . Virtually no loss of activity results after prolonged storage at -15 degrees . 4. Incubation of the bean enzyme with peptides indicates that the enzyme will release acidic, neutral and basic amino acid residues as well as proline, although adjacent acidic residues in a peptide appear to inhibit the enzyme. The possibility of endopeptidase activity in the purified preparation requires further examination.

Workgroup report: Indoor chemistry and health

Chemicals present in indoor air can react with one another, either in the gas phase or on surfaces, altering the concentrations of both reactants and products. Such chemistry is often the major source of free radicals and other short-lived reactive species in indoor environments. To what extent do the products of indoor chemistry affect human health? To address this question, the National Institute for Occupational Safety and Health sponsored a workshop titled "Indoor Chemistry and Health" on 12-15 July 2004 at the University of California-Santa Cruz. Approximately 70 experts from eight countries participated. Objectives included enhancing communications between researchers in indoor chemistry and health professionals, as well as defining a list of priority research needs related to the topic of the workshop. The ultimate challenges in this emerging field are defining exposures to the products of indoor chemistry and developing an understanding of the links between these exposures and various health outcomes. The workshop was a step toward meeting these challenges. This summary presents the issues discussed at the workshop and the priority research needs identified by the attendees.

Gas-phase chemistry of (alpha-terpineol with ozone and OH radical: rate constants and products

A bimolecular rate constant, kOH+alpha-terpineol, of (1.9 +/- 0.5) x 10(-10) cm3 molecule(-1) s(-1) was measured using gas chromatography/mass spectrometry and the relative rate technique for the reaction of the hydroxyl radical (OH) with alpha-terpineol (1-methyl-4-isopropyl-1-cyclohexen-8-ol) at (297 +/- 3) K and 1 atm total pressure. Additionally, a bimolecular rate constant, kO3+alpha-terpineol, of (3.0 +/- 0.2) x 10(-16) cm3 molecule(-1) s(-1) was measured by monitoring the first order decrease in ozone concentration as a function of excess alpha-terpineol. To better understand alpha-terpineol's gas-phase transformation in the indoor environment, the products of the alpha-terpineol + OH and alpha-terpineol + 03 reactions were also investigated. The positively identified alpha-terpineol/OH reaction products were acetone, ethanedial (glyoxal, HC(=O)C(=O)H), and 2-oxopropanal (methyl glyoxal, CH3C(=O)C(=O)H). The positively identified alpha-terpineol/O3 reaction product was 2-oxopropanal (methyl glyoxal, CH3C(=O)C(=O)H). The use of derivatizing agents O-(2,3,4,5,6-pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible alpha-terpineol/OH and alpha-terpineol/O3 reaction mechanisms based on previously published volatile organic compound/ OH and volatile organic compound/O3 gas-phase reaction mechanisms.

Histone variant H2A.Z is required for early mammalian development

Fundamental to the process of mammalian development is the timed and coordinated regulation of gene expression. This requires transcription of a precise subset of the total complement of genes. It is clear that chromatin architecture plays a fundamental role in this process by either facilitating or restricting transcription factor binding [1]. How such specialized chromatin structures are established to regulate gene expression is poorly understood. All eukaryotic organisms contain specialized histone variants with distinctly different amino acid sequences that are even more conserved than the major core histones [2]. On the basis of their highly conserved sequence, histone variants have been assumed critical for the function of mammalian chromatin; however, a requirement for a histone variant has not been shown in mammalian cells. Mice with a deletion of H1 degrees have been generated by gene targeting in ES cells, but these mice show no phenotypic consequences, perhaps due to redundancy of function [3]. Here we show for the first time that a mammalian histone variant, H2A.Z, plays a critical role in early development, and we conclude that this histone variant plays a pivotal role in establishing the chromatin structures required for the complex patterns of gene expression essential for normal mammalian development.

Esophageal dysmotility as an important co-factor in extraesophageal manifestations of gastroesophageal reflux

OBJECTIVE

Esophageal motility problems have been demonstrated in patients with noninflammatory typical gastroesophageal reflux (GER) and esophagitis, but the frequency of motility disorders in patients with extraesophageal manifestations of GER has not been studied. The primary aim of this study was to assess the frequency of esophageal motility disorders in patients with atypical GER.

METHODS

A prospective study of 112 consecutive patients with laryngopharyngeal reflux (LPR) symptoms and demonstrated physical findings consistent with LPR were studied. Patients were divided into one of the following diagnostic categories: hoarseness; chronic cough; dysphagia or globus pharyngeus; and paroxysmal laryngospasm. Of the 112 patients, 81 (72%) underwent esophageal manometry and ambulatory 24-hour pH monitoring (pH-metry), 19 (17%) had motility studies only, and 12 (11%) had pH-metry studies only. Only patients who had motility studies were included in the analysis. Therefore the study population was 100 patients. Associations between diagnostic category, motility disorder, and abnormal reflux were evaluated with contingency-table analyses.

RESULTS

Of the 100 patients, 29 (29%) presented normal motility function, 48 (48%) had ineffective esophageal motility, 10 (10%) had hypertensive lower esophageal sphincter (LES), and 9 (9%) and 4 (4%) had nutcracker esophagus and achalasia, respectively. There was a significant association between esophageal dysmotility and extraesophageal manifestations of GER However, there was no statistically significant association between esophageal motility disorders and abnormal acid reflux in our patients with atypical GER.

CONCLUSIONS

In the present study, the frequency of esophageal motility problems in patients with extraesophageal or atypical manifestations of GER was 73% and suggested that these problems exist as an accompanying condition or pathogenic co-factor in some patients with atypical GER.

Regions of variant histone His2AvD required for Drosophila development

One way in which a distinct chromosomal domain could be established to carry out a specialized function is by the localized incorporation of specific histone variants into nucleosomes. H2AZ, one such variant of the histone protein H2A, is required for the survival of Drosophila melanogaster, Tetrahymena thermophila and mice (R. Faast et al., in preparation). To search for the unique features of Drosophila H2AZ (His2AvD, also referred to as H2AvD) that are required for its essential function, we have performed amino-acid swap experiments in which residues unique to Drosophila His2AvD were replaced with equivalently positioned Drosophila H2A.1 residues. Mutated His2AvD genes encoding modified versions of this histone were transformed into Drosophila and tested for their ability to rescue null-mutant lethality. We show that the unique feature of His2AvD does not reside in its histone fold but in its carboxy-terminal domain. This C-terminal region maps to a short alpha-helix in H2A that is buried deep inside the nucleosome core.

A H1 histone gene-specific AC-box-related element influences transcription from a major chicken H1 promoter

In comparing several histone H1 promoters, we have identified a highly conserved sequence element, 5'-TGTGTTA, located approx. 450-480 bp upstream from the cap site. This TG-box is a near perfect inverted repeat of the previously characterized AC-box (5'-AAACACA). The distance between these elements is also highly conserved. We performed transient transfection assays with cat gene reporter constructs which indicated that both the presence and correct position of the TG-box were essential for maximal expression of the chicken 02 H1 promoter. To the best of our knowledge, this study represents the first demonstration of an effect by the TG-box on transcription of a major histone-encoding H1 gene.

An unusual arrangement of 13 zinc fingers in the vertebrate gene Z13

The zinc finger is a protein domain that imparts specific nucleic acid-binding activity on a wide range of functionally important proteins. In this paper we report the molecular cloning and characterization of a novel murine zinc-finger gene, mZ13. Analysis of mZ13 cDNAs revealed that the gene expresses a 794-amino-acid protein encoded by a 2.7 kb transcript. The protein has an unusual arrangement of 13 zinc fingers into a 'hand' of 12 tandem fingers and a single isolated finger near the C-terminus. This structural organization is conserved with the probable chicken homologue, cZ13. mZ13 also contained an additional domain at the N-terminus which has previously been implicated in the regulation of zinc-finger transcription factor DNA-binding, via protein-protein interactions. mZ13 expression was detected in a wide range of murine embryonic and adult tissues. The structural organization of mZ13 and its expression profile suggest that it may function as a housekeeping DNA-binding protein that regulates the expression of specific genes.

Evidence for involvement of the carboxy terminus of helix 1 of growth hormone in receptor binding: use of charge reversal mutagenesis to account for calcium dependence of binding and for design of higher affinity analogues

In this study we have demonstrated that the C-terminus of helix 1 of porcine GH (pGH) is a receptor-interactive region, thus extending the current binding site model of GH. This was achieved by introducing charge reversal mutations into this region of pGH, which influenced receptor affinity and Ca2+ dependence of binding. The first mutant (R34E pGH, conversion of Arg 34 to Glu) introduced a putative Ca2+ binding site which is present in human GH (hGH) [Barnard et al. (1989) J. Theor. Biol. 140, 355-367] and sits opposite E220 of receptor subunit 1. This mutant exhibited increased Ca2+ dependence of receptor binding but even at optimal Ca2+ did not display higher than wild-type affinity. Introduction of a second Ca2+ binding site adjacent to the first by a second charge reversal (K30E R34E pGH) further increased Ca2+ dependence of binding and also increased affinity for the rabbit GH receptor (2.4 +/- 0.4)-fold relative to wild-type pGH at optimal Ca2+. Equilibrium dialysis and Scatchard analysis of binding of 45Ca2+ to pGH and K30E R34E pGH revealed two Ca2+ binding sites on wild-type pGH and an additional two Ca2+ binding sites on the K30E R34E pGH mutant (Kd 0.5-0.8 mM), as predicted. A third partial charge reversal mutant in the fourth helix (H170D) also led to enhanced Ca2+ dependence of binding, supporting our proposal that E34 and D170 are responsible for the Ca2+ dependence of hGH binding to the rabbit GH receptor. Examination of the crystal structure shows that E34 and D170 are in close proximity and would interact repulsively with a cluster of acidic residues on the receptor consisting of E126, E127, and E220 unless neutralized by Ca2+ or an introduced basic residue. Accordingly, charge reversal at the adjacent pGH residue E33 (E33K pGH) led to a Ca2+ independent (3.0 +/- 0.4)-fold increase in affinity of binding. As well as extending the binding site model of GH, these studies provide a mechanistic explanation for the unique Ca2+ dependence of hGH binding to the rabbit GH receptor. They also indicate that charge reversal can be used to design higher affinity GH analogues and could assist in the mapping of interactive regions in ligand-receptor complexes generally.

Secretion of eukaryotic growth hormones in Escherichia coli is influenced by the sequence of the mature proteins

We report the construction of secretion plasmids expressing the fusion proteins, OmpA::pGH (pSpGH.01) and OmpA::hGH (phGH.01), and compare the secretion of mature porcine growth hormone (pGH) and human growth hormone (hGH) employing Escherichia coli. E. coli [phGH.01] secreted 10-15 micrograms hGH/ml/A600 cells into the periplasmic space, representing 30% of total periplasmic proteins. E. coli [pSpGH.01], however, secreted 30-fold less mature pGH. On the basis that both pSpGH.01 and phGH.01 are stably maintained in E. coli and in vitro transcription/translation data showed equivalent expression of OmpA::pGH and OmpA::hGH precursors, we attribute the higher secretion of hGH to the translocation-competent OmpA::hGH protein configuration. Two OmpA::GHF (growth hormone fusion) precursors, OmpA::GHF.02 and OmpA::GHF.03, both with hGH helix 3/helix 4 together instead of the pGH equivalent, secreted mature proteins as efficiently as OmpA::hGH. We propose that hGH helices 3 and 4 in these OmpA::GHF precursors play a major role in the folding of the precursor to a translocation-competent state, mimicking the translocation-competent nature of the OmpA::hGH precursor.

Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency

An efficient expression system in Escherichia coli for several biologically active insulin-like growth factor-I (IGF-I) fusion peptide analogues is described. These novel IGF-I fusion protein analogues have properties that make them very useful reagents in the investigation of IGF-I action. The analogues comprise an IGF-I sequence and the first 11 amino acids of methionyl porcine growth hormone (pGH) and include [Met1]-pGH(1-11)-Val-Asn-IGF-I, which contains the authentic IGF-I sequence, and two analogues, [Met1]-pGH(1-11)-Val-Asn-[Gly3]-IGF-I and [Met1]-pGH(1-11)-Val-Asn-[Arg3]-IGF-I, where Glu-3 in the human IGF-I sequence has been replaced by Gly or Arg respectively. The three peptides are referred to as Long IGF-I, Long [Gly3]-IGF-I or Long [Arg3]-IGF-I depending on the IGF-I sequence present. Production of the purified fusion peptides was aided by folding the reduced and denatured fusion peptide sequence under conditions that gave very high yields of biologically active product. Introduction of a hydrophobic N-terminal extension peptide appears to facilitate the correct folding of the IGF-I analogues compared with that obtained previously when folding normal-length IGFs. The biological activities of the IGF-I fusion peptides were compared with authentic IGF-I and the truncated analogue, des(1-3)IGF-I. In L6 rat myoblasts, all the analogues were more potent than authentic IGF-I in their abilities to stimulate protein and DNA synthesis and inhibit protein breakdown. In H35 hepatoma cells, where the IGFs act through the insulin receptor, the Long IGF-I analogues maintained a similar potency relative to IGF-I as was observed in the L6 myoblasts. The order of biological potency in cell lines secreting IGF-binding proteins (IGFBPs) into the medium was Long [Arg3]-IGF-I-des(1-3)IGF-I greater than Long [Gly3]-IGF-I greater than Long IGF-I greater than IGF-I. In chicken embryo fibroblasts, a cell line that does not secrete detectable IGFBPs into the medium, Long [Arg3]-IGF-I, was less potent than IGF-I. Investigation of receptor and IGFBP association by these analogues reinforced our previous findings that N-terminal analogues of IGF-I show increased biological potency due to changes in the degree of their IGFBP interactions.

Sequence of a cDNA encoding chicken high-mobility-group protein-2

There are several members of the high-mobility-group (HMG) of DNA-binding proteins, including HMG-1, HMG-2, HMG-14 and HMG-17 [Johns: The HMG Chromosomal Proteins. Academic Press, London, 1982]. We report here sequences encoding the chicken HMG-2 protein of 207 amino acids (aa). This assignment is made on the basis of available data which indicate 89% homology of the chicken aa sequence to porcine HMG-2. This compares with 78-81% homology to the HMG-1 proteins of rat, hamster, human, porcine, and bovine origin.

Production and characterization of recombinant insulin-like growth factor-I (IGF-I) and potent analogues of IGF-I, with Gly or Arg substituted for Glu3, following their expression in Escherichia coli as fusion proteins

The development of an efficient expression system for insulin-like growth factor-I (IGF-I) in Escherichia coli as a fusion protein is described. The fusion protein consists of an N-terminal extension made up of the first 46 amino acids of methionyl porcine GH ([Met1]-pGH) followed by the dipeptide Val-Asn. The latter two residues provide a unique hydroxylamine-sensitive link between [Met1]-pGH(1-46) and the N-terminal Gly of IGF-I. Downstream processing of the fusion proteins involved isolation of inclusion bodies, cleavage at the Asn-Gly bond, refolding of the reduced IGF-I peptide and purification to homogeneity. This expression system was also used to produce two variants of IGF-I in which Glu3 was substituted by either Gly or Arg to give [Gly3]-IGF-I and [Arg3]-IGF-I respectively. Production of milligram quantities of IGF-I peptide was readily achieved. The purity of the IGF-I, [Gly3]-IGF-I and [Arg3]-IGF-I was established by high-performance liquid chromatography and N-terminal sequence analysis. [Gly3]-IGF-I and [Arg3]-IGF-I were more potent than IGF-I in biological assays measuring stimulation of protein synthesis and DNA synthesis or inhibition of protein breakdown in rat L6 myoblasts. Both analogues bound very poorly to bovine IGF-binding protein-2 and slightly less well than IGF-I to the type-1 receptor on rat L6 myoblasts. We conclude that reduced binding to IGF-binding proteins rather than increased receptor binding is the likely explanation for the greater biological potency of the analogues compared with IGF-I.

Identification of molecules involved in the 'early pregnancy factor' phenomenon

An isolated preparation from ovine placental extracts which was active in the rosette inhibition assay mimicking the activity of the so-called 'early pregnancy factor' (EPF) has been shown to contain a 12 kDa polypeptide which could be partially resolved from low-molecular-weight active moieties. N-terminal amino acid sequence analysis of the polypeptide indicated that it was ovine thioredoxin, an identification confirmed by isolation and complete sequence analysis of the corresponding cDNA. The cDNA for human thioredoxin was expressed in Escherichia coli and the recombinant protein isolated and purified. Pure recombinant thioredoxin alone did not induce the expression of increased rosette inhibition titres (RITs) when tested in the rosette inhibition assay; but, when tested in combination with cell stimuli such as platelet-activating factor (PAF) or serum, it allowed the expression of increased RITs where none was achieved in its absence. Thioredoxin acted in the assay to reverse a refractory state normally induced by these stimuli, allowing lipoxygenase-dependent moieties also induced by the stimuli to exert their effects, resulting in the expression of increased RITs. Antibodies to recombinant thioredoxin removed from pregnancy sera the capacity to induce increased RITs, i.e. to express EPF activity, thus establishing a role for thioredoxin or thioredoxin-like proteins and associated molecules in the mechanisms which allow pregnancy sera to induce increased RITs. Based on a consideration of these and other results, a new model for the study of the EPF phenomenon is presented and discussed.

Isolation and characterization of human thioredoxin-encoding genes

Thioredoxin (Trx) has recently been demonstrated to be an essential component of the early pregnancy factor activity of pregnancy serum. Here, we report the structure and sequence of human Trx-encoding genes (Trx) by analysis of genomic clones. The Trx gene extends over 13 kb and consists of five exons encoding a 12-kDa protein. A 700-bp fragment upstream from the start codon functions as a promoter when inserted in front of a human growth hormone-encoding reporter gene in tissue-culture cells. This promoter region is very G + C rich and does not contain a classical TATA or CCAAT box, but has three consensus sequences for high-affinity Sp1 binding. Southern analysis demonstrated the presence of several Trx genes in the human genome. The number includes at least one inactive copy as shown by the isolation and sequencing of an inactive pseudogene.

Expression, purification and characterization of secreted recombinant human insulin-like growth factor-I (IGF-I) and the potent variant des(1-3) IGF-I in Chinese hamster ovary cells

Recombinant human insulin-like growth factor-I (hIGF-I) and a biologically potent variant lacking the N-terminal tripeptide (des(1-3)IGF-I) were produced from transfected Chinese hamster ovary cells. The constructs encoding the signal peptide, sequence of the mature peptide and a C-terminal extension peptide were expressed under the control of a Rous sarcoma virus promoter. Successfully transfected clones secreting correctly processed recombinant hIGF-I or des(1-3)IGF-I were selected by their secretion of IGF-I-like activity into the culture medium. The recombinant peptides were purified to homogeneity as assessed by high-performance liquid chromatography and N-terminal sequence analysis. The purified recombinant peptides exhibited biological potencies equivalent to authentic IGF-I and des(1-3)IGF-I respectively.