Optical trapping and Raman spectroscopy of solid particles.

The heterogeneous interactions of gas molecules on solid particles are crucial in many areas of science, engineering and technology. Such interactions play a critical role in atmospheric chemistry and in heterogeneous catalysis, a key technology in the energy and chemical industries. Investigating heterogeneous interactions upon single levitated particles can provide significant insight into these important processes. Various methodologies exist for levitating micron sized particles including: optical, electrical and acoustic techniques. Prior to this study, the optical levitation of solid micron scale particles has proved difficult to achieve over timescales relevant to the above applications. In this work, a new vertically configured counter propagating dual beam optical trap was optimized to levitate a range of solid particles in air. Silica (SiO2), α-alumina (Al2O3), titania (TiO2) and polystyrene were stably trapped with a high trapping efficiency (Q = 0.42). The longest stable trapping experiment was conducted continuously for 24 hours, and there are no obvious constraints on trapping time beyond this period. Therefore, the methodology described in this paper should be of major benefit to various research communities. The strength of the new technique is demonstrated by the simultaneous levitation and spectroscopic interrogation of silica particles by Raman spectroscopy. In particular, the adsorption of water upon silica was investigated under controlled relative humidity environments. Furthermore, the collision and coagulation behaviour of silica particles with microdroplets of sulphuric acid was followed using both optical imaging and Raman spectroscopy.

Heterogeneous interaction of SiO2 with N2O5: aerosol flow tube and single particle optical levitation-Raman spectroscopy studies.

Silica (SiO2) is an important mineral present in atmospheric mineral dust particles, and the heterogeneous reaction of N2O5 on atmospheric aerosol is one of the major pathways to remove nitrogen oxides from the atmosphere. The heterogeneous reaction of N2O5 with SiO2 has only been investigated by two studies previously, and the reported uptake coefficients differ by a factor of >10. In this work two complementary laboratory techniques were used to study the heterogeneous reaction of SiO2 particles with N2O5 at room temperature and at different relative humidities (RHs). The uptake coefficients of N2O5, γ(N2O5), were determined to be (7.2 ± 0.6) × 10(-3) (1σ) at 7% RH and (5.3 ± 0.8) × 10(-3) (1σ) at 40% RH for SiO2 particles, using the aerosol flow tube technique. We show that γ(N2O5) determined in this work can be reconciled with the two previous studies by accounting for the difference in geometric and BET derived aerosol surface areas. To probe the particle phase chemistry, individual micrometer sized SiO2 particles were optically levitated and exposed to a continuous flow of N2O5 at different RHs, and the composition of levitated particles was monitored online using Raman spectroscopy. This study represents the first investigation into the heterogeneous reactions of levitated individual SiO2 particles as a surrogate for mineral dust. Relative humidity was found to play a critical role: while no significant change of particle composition was observed by Raman spectroscopy during exposure to N2O5 at RH of <2%, increasing the RH led to the formation of nitrate species on the particle surface which could be completely removed after decreasing the RH back to <2%. This can be explained by the partitioning of HNO3 between the gas and adsorbed phases. The atmospheric implications of this work are discussed.

Evaluation of laboratory kinetics and photochemical data for atmospheric chemistry applications.

This article deals with the evaluation of chemical kinetics and photochemical data for use in atmospheric modeling. Models used to calculate the temporal and spatial variation of atmospheric trace gas composition are based on chemical schemes which require chemical kinetics data for the elementary reactions involved. These data derive from careful experimentation under conditions relevant for the atmosphere, carried out in laboratories worldwide using ever improving technology over the past 50 years. The article contains an account of the background issues of atmospheric composition change which have stimulated this branch of atmospheric science; this is followed by a section on parameterisation and evaluation of kinetics data. A description of currently available on-line databases is provided. The final section contains a short description of some recent significant improvement in knowledge of rate constants for key reactions of interest in stratospheric and tropospheric chemistry.

Temperature dependent structured absorption spectra of molecular chlorine.

A dual wavelength range spectrometer system has been designed and constructed which can simultaneously perform single pass UV absorption spectroscopy and cavity enhanced absorption spectroscopy in the green region of the visible spectrum. Using the system the absorption spectrum of molecular chlorine has been measured, in the wavelength range 509-570 nm, using cavity enhanced absorption spectroscopy. Absolute absorption cross sections were obtained by simultaneous measurement of the UV spectrum to obtain the Cl(2) concentration. These are the first temperature dependent measurements of the Cl(2) absorption cross sections in this region which are vibronically resolved. Laboratory measurements were conducted at four temperatures (298, 273, 233, and 197 K). Spectral modelling of the Cl(2) B(3)Π(0(u)(+))-X(1)Σ(g)(+) electronic transition has been performed, the results of which are in good agreement with our measured spectra.

Pre-clinical evaluation of liposomal gene transfer to improve dermal and epidermal regeneration.

Liposomal gene transfer effectively enhances dermal and epidermal regeneration in burned rodents. To advance this treatment to clinical studies, we investigated the efficacy of liposomal gene transfer in a clinically relevant porcine wound model. Mimicking the clinical scenario, six female Yorkshire pigs (40-50 kg) received up to 12 burns of 50 cm(2) area that were fully excised and covered with skin autograft meshed at 4:1 ratio 24 h post-burn. Animals received control injections (empty liposomes), liposomes (DMRIE-C) containing 1 mg LacZ-cDNA, or liposomes (DMRIE-C) with 1 mg of platelet-derived growth factor (PDGF)-cDNA, or the naked PDGF gene. Serial biopsies were taken from different wound sites at multiple time points up to 12 days post-wounding. Transfection efficacy and transfection rate of LacZ and localization of beta-gal were determined by immunohistochemical and immunofluorescent techniques. RT-PCR and multiplex protein analysis (ELISA) were used to measure levels of growth factor mRNA transcribed and growth factor protein translated. Wound re-epithelialization and graft adhesion was evaluated using planimetric analysis and clinical scores. We found that peak transfection of liposomal beta-galactosidase occurred on day 2, with a fluorescence increase of 154% to baseline (P<0.001). Transfection intensity dropped to 115% above baseline on day 4 (P<0.001) and 109% on day 7. Immunohistochemistry showed a maximum transfection rate of 34% of cells in wound tissue. Gene transfer of liposomal PDGF-cDNA resulted in increased PDGF-mRNA and protein expression on days 2 and 4, and accelerated wound re-epithlialization as well as graft adhesion on day 9 (P<0.05). In this study, we showed that liposomal cDNA gene transfer is possible in a porcine wound model, and by using PDGF-cDNA we further showed that dermal and epidermal regeneration can be improved. These data indicate that liposomal gene transfer can be a new therapeutic approach to improve wound healing in humans.

Ozonolysis of maleic acid aerosols: effect upon aerosol hygroscopicity, phase and mass.

The hygroscopicity and mass loss of aerosols initially composed of maleic acid have been investigated before and after reaction with ozone. The phase of the aerosol, solid or aqueous, during the reaction with ozone strongly affects the composition of the processed aerosol. Furthermore the loss of aerosol mass, via the production of volatile ozonolysis products, does not occur until the processed aerosol has existed as an aqueous phase aerosol. The loss rate of the aerosol mass appears to follow unimolecular first order kinetics which is consistent with the rate determining step being the cleavage of a weak hydroperoxide, or peroxide, bond (approximately 104 kJ mol(-1)). This speculative rate determining step, which is not based on chemical analysis, is possibly a universal feature in the ozonolysis of organic aerosol containing the alkene functionality.

Release of gas-phase halogens by photolytic generation of OH in frozen halide-nitrate solutions: an active halogen formation mechanism?

To better define the mechanisms by which condensed-phase halides may be oxidized to form gas-phase halogens under polar conditions, experiments have been conducted whereby frozen solutions containing chloride (1 M), bromide (1.6 x 10(-3) to 5 x 10(-2) M), iodide (<1 x 10(-5) M), and nitrate (0.01 to 1 M) have been illuminated by ultraviolet light in a continually flushed cell. Gas-phase products are quantified using chemical ionization mass spectrometry, and experiments were conducted at both 248 and 263 K. Br(2) was the dominant product, along with smaller yields of IBr and trace BrCl and I(2). The Br(2) yields were largely independent of the Br(-)/Cl(-) ratio of the frozen solution, down to seawater composition. However, the yields of halogens were strongly dependent on the levels of NO(3)(-) and acidity in solution, consistent with a mechanism whereby NO(3)(-) photolysis yields OH that oxidizes the condensed-phase halides. In support, we observed the formation of gas-phase NO(2), formed simultaneously with OH. Gas-phase HONO was also observed, suggesting that halide oxidation by HONO in the condensed phase may also occur to some degree. By measuring the production rate of condensed-phase OH, using benzoic acid as a radical trap, we determine that the molar yield of Br(2) formation relative to OH generation is 0.6, consistent with each OH being involved in halide oxidation. These studies suggest that gas-phase halogen formation should occur simultaneously with NO(x) release from frozen sea ice and snow surfaces that contain sufficient halides and deposited nitrate.

Circulating immune complexes in coccidioidomycosis. Detection and characterization.

Sera of 22 patients with active and 13 with inactive coccidioidomycosis, as well as 15 healthy subjects who were skin-test positive to coccidioidin and 39 healthy subjects who were coccidioidin skin-test negative, were assayed for immune complexes. Circulating immune complexes were measured by the Clq-binding assay, the Clq-solid phase assay, the monoclonal rheumatoid factor inhibition assay, and the monoclonal rheumatoid factor solid phase assay. An increased concentration of circulating immune complexes was detected in 73% of those with active disease by at least one assay compared with 13% of the healthy controls. Significantly increased levels of immune complexes were detected in sera of patients with active coccidioidomycosis by the Clq-binding assay (P < 0.001), the Clq-solid phase assay (P < 0.001), the monoclonal rheumatoid factor inhibition assay (P < 0.005), and the monoclonal rheumatoid solid phase assay (P < 0.05) compared with the results obtained in the 54 healthy subjects. In contrast, those with inactive disease did not show significantly increased concentrations of circulating immune complexes. Sucrose density gradient ultracentrifugation of patients' sera established that the immune complexes were of intermediate size, sedimenting between the 6.6S and 19S markers. Immune complexes were shown to contain both coccidioidin antigen and anticoccidioidin antibody. In addition, a radioimmunoassay was developed to quantitate coccidioidin antigen-containing immune complexes. The latter assay proved highly sensitive in detecting immune complexes in patients with active coccidioidomycosis.

Effect of simian virus 40 subcutaneous tumors on circulating lipids and lipoproteins in the Syrian hamster.

Circulating lipid levels and lipoprotein patterns in the Syrian hamster were determined at various times after subcutaneous inoculation with simian virus 40 (SV40) strain F, strain A-2895, or Fortner melanoma tumor cells. SV40 F tumors induced a rapid triphasic elevation of serum total lipids through inhibition of prebeta lipoprotein catabolism. Alpha lipoprotein levels declined in proportion to tumor mass. Liver wet weight and total lipid content increased significantly, but a normal rate of 3H-glycerol incorporation into polyanion precipitable (prebeta) serum lipoprotein was maintained. Determination of serum endogenous lipase, lecithin:cholesterol acyltransferase (LCAT), and cholinesterase activities indicated that these enzymes were not primarily responsible for the tumor-induced hyperlipidemia. Tumor-bearing animals also had selectively increased rates of protein and lipid excretion into the urine, with no evidence of gross hepatocellular or kidney damage. Growth of SV40 A-2895 tumors in hamsters resulted in a large increase in the rate of prebeta lipoprotein synthesis and degradation. Circulating prebeta lipoprotein levels were elevated much later in these animals, subsequent to a marked decrease in LCAT activity. Quite different results were obtained with Fortner melanoma, even large tumors having only a moderate effect on serum total lipid levels and lipoprotein patterns in the Syrian hamster.

Solution of ribosomal proteins under mild conditions.

Ribosomal proteins from two eucaryotic species, prepared by either the guanidine . HCl or LiCl . urea method and subsequently dissolved in 8 M urea were found to be largely retained in solution after removal of the urea by dialysis against a solution of low ionic strength (0.05 M Tris . HCl, pH 7.6, 0.025 M KCl, 0.005 M magnesium acetate) and centrifugation at 100,000 times g. The protein composition of this preparation was virtually identical to that of the original urea-containing solution as determined by two-dimensional polyacrylamide gel electrophoresis. Thus, there exists a very simple method for obtaining the bulk of the ribosomal proteins in solution under conditions where ribosomes themselves are stable.

Primary structure of an alpha-tubulin gene of Physarum polycephalum.

An alpha-tubulin gene of Physarum was isolated as a phage-lambda NM1149 recombinant (designated phage-lambda N alpha Tu). Phage-lambda N alpha Tu contained a 4700 base-pair HindIII nuclear DNA fragment of an allele of the altB locus of Physarum (one of four unlinked alpha-tubulin gene loci). Subfragments of the 4700 base-pair insert of phage-lambda N alpha Tu were cloned into phage M13 and the nucleotide sequence was determined by the dideoxy chain termination method. The start point of transcription was identified by primer extension and a putative polyadenylation site was located by S1 nuclease analysis. The 4650 base-pair HindIII insert into phage-lambda N alpha Tu spans the complete gene; sequences upstream from the 5' end contain the RNA transcription promoter elements (the TATA and CCAAT boxes). The nucleotide sequence encoding alpha-tubulin contains seven intervening sequences, ranging from 63 to 222 nucleotides in size. The exons have a sequence that is identical with a Physarum alpha-tubulin cDNA clone, except for three base changes, one leading to a Val codon in place of a Met codon, another leading to a Glu codon in place of an Asp codon, and the third change is silent. The genomic clone provides the nucleotide sequence coding for the last 26 amino acid residues missing from the cDNA clone. The new sequence data indicate that the alpha-tubulin gene has a C-terminal methionine codon and not a tyrosine codon, which has been found in all alpha-tubulin genes sequenced to date.

Structure and expression of an actin gene of Physarum polycephalum.

Physarum polycephalum (strain M3CVIII) contains four unlinked actin gene loci, each with two alleles (ardA1, ardA2, ardB1, ardB2, ardC1, ardC2, ardD1 and ardD2). The 4800 base HindIII fragment of the ardC2 allele was previously isolated as a recombinant phage lambda. We now report the structure of the actin gene sequences (C-actin gene). The gene, which contains four intervening sequences, codes for the principal actin isotype of plasmodia and it is expressed in both the haploid myxamoebal and diploid plasmodial phases of the life cycle. The C-actin isotype is closely related to actins of Dictyostelium, Acanthamoebae, Drosophila, sea urchin and mammalian cytoplasmic actin, and more distantly related to actins of yeast, Entamoebae and Tetrahymena. The ardC1 and ardC2 alleles differ by a 700(+/- 100) base-pair insertion/deletion in the vicinity of the 3' end of the transcribed region of the gene.

Coccidioides immitis antigen 2: analysis of gene and protein.

Antigen 2 is a glycosylated protein present in the cell walls of the dimorphic fungus Coccidioides immitis. Using oligodeoxyribonucleotide (oligo) primers based on the sequences of Ag2 cDNA, the gene encoding Ag2 was cloned from genomic DNA derived from the mycelial phase of C. immitis by PCR. Nucleotide (nt) sequence analyses showed a 582 base pair (bp) ORF disrupted by two introns which are 78 bp and 101 bp long. The deduced primary translation product consists of 194 amino acids (aa), contains an N-terminal putative signal sequence to allow transport into the endoplasmic reticulum, and a C-terminal putative signal sequence to enable a GPI anchor addition. Putative GPI anchor/cleavage site and O-glycosylation sites, as well as phosphorylation and myristoylation sites are also present. On the basis of these analyses, we predict that a prepro-Ag2 undergoes a post-translational modification to yield the mature glycosylated Ag2 protein which is anchored on the extracellular plasma membrane of mycelial and spherule-phase cells.

Evidence for genetic divergence in ribosomal RNA genes in mycobacteria.

DNA was isolated from Mycobacterium phlei and from M. smegmatis. Each DNA sample was restricted with endonucleases, the fragments were separated by agarose gel electrophoresis and transferred to nitrocellulose film. Fragments of DNA containing rRNA sequences were identified by means of 125I-labelled rRNA of M. phlei or of M. smegmatis. The distributions of restriction endonuclease sites within the rRNA gene(s) and flanking sequences were found to be characteristic for each of the two species. Hybridizations with heterologous probes indicate that although M. phlei rRNA and M. smegmatis rRNA share regions of sequence homology, they are probably not identical in primary structure. The results suggest that the rRNA genes might prove to be useful taxonomic markers for mycobacteria.

Differential expression of an alpha-tubulin gene during the development of Physarum polycephalum.

The expression of an alpha-tubulin gene (altB1 (N alpha Tu) [(1987) J. Mol. Biol. 193, 427-438]) of Physarum polycephalum (strain CLdAXE) was found to be governed by a developmental switch since mRNA transcripts were detected, by S1 nuclease analysis, in the plasmodial but not the amoebal phase of the life-cycle. The conclusion that the altB1 (N alpha Tu) allele codes for a plasmodial specific alpha-tubulin isotype is supported by recent amino acid sequence data.

Identification of EcoRV fragments spanning the N alpha-tubulin gene of Physarum.

The N alpha-tubulin gene of Physarum polycephalum has an EcoRV site at codons 252/253. EcoRV digestion of physarum DNA generated two EcoRV fragments per gene copy comprising both coding and flanking sequences. Hybridisation probes which included coding sequences upstream from the central EcoRV site cross-hybridised with another alpha-tubulin gene. Probes derived from either 5'- or 3'-flanking regions were gene-specific. These probes identified two EcoRV fragments in the haploid strain CLdAXE viz 5.4 kb (5'-fragment) and 6.2 kb (3'-fragment). The same two fragments were identified in EcoRV digests of DNA of the diploid strain M3CVIII, and a second form of the gene was also identified comprising two fragments viz 5.0 kb (5'-end) and 5.5 kb (3'-end). Both forms gave rise to an identical 4.65 kb HindIII fragment as judged by restriction mapping.

Biosynthesis and activity of DNA polymerase throughout the mitotic cycle of Physarum polycephalum.

Measurements of DNA polymerase protein levels and polymerase activity through the naturally synchronous mitotic cycle of Physarum polycephalum show that active DNA polymerase-alpha is synthesized throughout the G2 phase, in step with the profile of general protein biosynthesis. Three main components of P. poly-cephalum DNA polymerase of 200, 112 and 70 kDa were found to be immunologically related.

Massive pulmonary embolism associated with a right ventricular myxoma.

A 12 year old boy had a massive pulmonary embolism associated with a right ventricular myxoma. This caused complete occlusion of the main trunk of the left pulmonary artery and of a branch of the right pulmonary artery supplying the basal area of the lower lobe of the right lung. The patient died despite two surgical attempts to remove the tumor clots. To our knowledge this constitutes the first report of a massive pulmonary artery embolism associated with a right ventricular myxoma.

Production of tumor necrosis factor-alpha and interleukin-1 by alveolar macrophages from HIV-1-infected persons.

Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) are potent immunomodulatory cytokines which are produced principally by cells of the macrophage-monocyte lineage. We conducted an investigation to assess the secretion of these cytokines by bronchoalveolar macrophages from patients with progressive stages of human immunodeficiency virus (HIV-1) infection. The mean level of TNF-alpha produced by macrophages from 9 patients with AIDS was significantly reduced compared with the responses of macrophages from 6 healthy HIV-1-seronegative persons, 6 patients with either asymptomatic HIV-1 infection or persistent generalized lymphadenopathy, and 6 patients with AIDS-related complex (ARC). The four study groups did not differ in their mean IL-1 beta responses. However, within the HIV-1-infected patient population, macrophages from 4 patients, 3 of whom had AIDS and 1 with ARC, failed to secrete detectable levels of IL-1 beta. All 4 patients were also nonresponsive in assays for TNF-alpha. These data establish that advanced HIV-1 infection may result in a pronounced dysfunction in the cytokine responses of alveolar macrophages.