Safe, convenient, portable pipettor

A dafe, convenient, portable pipetting device that will accommodate any size pipette is described. A vacuum bulb eliminates the need for external vacuum. Necessary components, fabrication procedures, and operating techniques are given.     

Drying of Tribenuron,a Thermosensitive Biochemical

The extension of microwave use in the biochemical industry was explored by drying tribenuron, a thermosensitive biochemical, in a microwave oven and in a thermal vacuum oven. Tribenuron wet cakes, containing a mixture of solvents, methanol and water, were heated at 40 °C in both ovens. Nitrogen purge was used to prevent the decomposition of tribenuron from prolonged heating. Microwave heating dried tribenuron in twenty minutes while the vacuum oven heating required eighteen hours to dry the wet cakes. In addition, the tribenuron quality was maintained under microwave drying, but deteriorated in the thermal vacuum oven. Therefore, microwave technology is more effective in drying tribenuron than conventional vacuum ovens. The results of this study are important for the use of microwave drying on a large scale in biochemical companies.     

Preservation of Claviceps purpurea, the producer of peptide ergot alkaloids, by the method of freeze drying

A saprotrophic strain of Claviceps purpurea VNIIA 312A, an organism producing peptide +ergot alkaloids with prolactin inhibiting activity was shown to die under lyophilization conditions. To provide long-term storage of strain 312A, L-drying or drying under vacuum from liquid state was used with success. Three protective media were tested. Favourable results were obtained by using 25 per cent maltose solution as a protective medium. Preservation of the culture viability was accompanied by maintenance of the culture capacity for active formation of the biomass and production of +ergot alkaloids.     

Molecular dynamics simulations of an enzyme surrounded by vacuum, water, or a hydrophobic solvent.

We report on molecular dynamics simulations of a medium-sized protein, a lipase from Rhizomucor miehei, in vacuum, in water, and in a nonpolar solvent, methyl hexanoate. Depending on force field and solvent, the molecular dynamics structures obtained as averages over 150 ps had root-mean-square deviations in the range of 1.9 to 3.6 A from the crystal structure. The largest differences between the structures were in hydrogen bonding and exposed surface areas of the protein. The surface area increased in both solvents and became smaller in vacuum. The change of surface exposure varied greatly between different residues and occurred in accordance with the hydrophobicity of the residue and the nature of the solvent. The fluctuations of the atoms were largest in the external loops and agreed well with crystallographic temperature factors. Root-mean-square fluctuations were significantly smaller in the nonpolar solvents than they were in water, which is in accordance with the notion that proteins become more rigid in nonpolar solvents. In methyl hexanoate a partial opening of the lid covering the active site occurred, letting a methyl hexanoate molecule approach the active site.     

Ultrastructural observations on tissues processed by a quick-freezing,rapid-drying method: Comparison with conventional specimen preparation

A quick-freeze, rapid-dry method for processing unfixed tissue for electron microscopy has been developed. The technique employs freezing on a cryogenchilled metal surface and drying in a cryosorption vacuum apparatus that allows osmium-vapor fixation and epoxy-resin embedment under high vacuum. Liver, kidney, bone marrow, and monolayer cultures of ventricular myocytes were selected as tissue specimens representing a wide range of physical properties, to demonstrate the practical aspects of achieving good ultrastructural morphology by freeze drying. A comparison was made between freeze drying and conventional processing using aldehyde fixation and alcohol dehydration. The preservation of cellular ultrastructure achieved by freeze drying allowed the identification of specific cell types within each specimen. Membranous organelles were well preserved, surrounded by cytoplasmic ground substance devoid of ice crystal damage. Electron-dense material was observed within the rough endoplasmic reticulum and Golgi cisternae and vesicles of frozen-dried, but not conventionally processed cells. This suggests the preservation by freeze drying of cytoplasmic components otherwise extracted from the cell by solvent exposure.     

Sampling methods, dispersion patterns, and fixed precision sequential sampling plans for western flower thrips (Thysanoptera: Thripidae) and cotton fleahoppers (Hemiptera: Miridae) in cotton

A 2-yr field study was conducted to examine the effectiveness of two sampling methods (visual and plant washing techniques) for western flower thrips, Frankliniella occidentalis (Pergande), and five sampling methods (visual, beat bucket, drop cloth, sweep net, and vacuum) for cotton fleahopper, Pseudatomoscelis seriatus (Reuter), in Texas cotton, Gossypium hirsutum (L.), and to develop sequential sampling plans for each pest. The plant washing technique gave similar results to the visual method in detecting adult thrips, but the washing technique detected significantly higher number of thrips larvae compared with the visual sampling. Visual sampling detected the highest number of fleahoppers followed by beat bucket, drop cloth, vacuum, and sweep net sampling, with no significant difference in catch efficiency between vacuum and sweep net methods. However, based on fixed precision cost reliability, the sweep net sampling was the most cost-effective method followed by vacuum, beat bucket, drop cloth, and visual sampling. Taylor's Power Law analysis revealed that the field dispersion patterns of both thrips and fleahoppers were aggregated throughout the crop growing season. For thrips management decision based on visual sampling (0.25 precision), 15 plants were estimated to be the minimum sample size when the estimated population density was one thrips per plant, whereas the minimum sample size was nine plants when thrips density approached 10 thrips per plant. The minimum visual sample size for cotton fleahoppers was 16 plants when the density was one fleahopper per plant, but the sample size decreased rapidly with an increase in fleahopper density, requiring only four plants to be sampled when the density was 10 fleahoppers per plant. Sequential sampling plans were developed and validated with independent data for both thrips and cotton fleahoppers.     

Lyophilization, vacuum drying, and subsequent storage of Nosema pyrausta spores

Methods of preserving Nosema pyrausta spores were developed by subjecting laboratoryreared, nondiapausing larvae of the European corn borer, Ostrinia nubilalis, infected with N. pyrausta to different techniques of lyophilization and vacuum drying. Such material was still viable when it was stored in an airtight container and held at ?12°C for 12 months, or when it was stored in a vacuum desiceator and held at 22–24°C for 6 months.     

Quenching of an electric arc in a vacuum gap with a uniform transverse magnetic field

The breaking ability of a vacuum arc interrupter with a uniform transverse magnetic field formed by a system of permanent magnets was investigated experimentally. The vacuum interrupter with a 0.5-μF shunting capacitor switched off a dc current of up to 150 A at magnetic fields of 100–180 mT. At magnetic fields of 120–160 mT, the breaking ability of the vacuum interrupter was increased to 300 A by introducing a nonuniformity in the magnetic field distribution near the contact surface.     

Oligomeric state investigation of flavocytochrome CYP102A1 using AFM with standard and supersharp probes

Atomic force microscopy with two types of probes—standard (radius of curvature R ∼ 10 nm) and supersharp (R ∼ 2 nm)—was used to determine an oligomeric state of CYP102A1. Using the standard probes CYP102A1 images were obtained in liquid, air and vacuum environments, and a CYP102A1 monomer: oligomer ratio α ≈ 1 was also determined. However, the use of standard probes did not allow to resolve structures of these oligomers. Using the supersharp probes it was possible to determine not only the monomer: oligomer ratio, but also to evaluate the dimer: trimer: tetramer ratio in vacuum. Thus, the ratio α for CYP102A1 in liquid can be determined by the standard probes in liquid, air, and vacuum, while oligomeric states of this protein can be specified by using the supersharp probes in vacuum.     

Ramachandran free-energy surfaces for disaccharides: trehalose, a case study

We present calculated potential of mean force surfaces for rotation about phi, psi dihedral angles of the alpha(1<-->1)alpha-glycosidic linkage in the disaccharide trehalose (alpha-D-Glc-(1<-->1)-alpha-D-Glc) in both vacuum and aqueous solution. The effects of aqueous solvation upon the alpha(1<-->1)alpha-glycosidic linkage are investigated through comparison of the vacuum and aqueous solution free-energy surfaces. These surfaces reveal that trehalose is restricted to a single minimum-energy conformation in both vacuum and solution. The exceptional rigidity of this disaccharide in solution may provide a molecular rationale for the antidesiccant properties of trehalose glasses.     

Transient gene expression in maize, rice, and wheat cells using an airgun apparatus

An airgun apparatus has been constructed for transient gene expression studies of monocots. This device utilizes compressed air from a commercial airgun to propel macroprojectile and DNA-coated tungsten particles. The β-glucuronidase (GUS) reporter gene was used to monitor transient expression in three distinct cell types of maize (Zea mays), rice (Oryza sativa), and wheat (Triticum aestivum). The highest level of GUS activity in cultured maize cells was observed when distance between stopping plate and target cells was adjusted to 4.3 centimeters. Efficiency of transformation was estimated to be 4.4 × 10⁻³. In a partial vacuum of 700 millimeters Hg, velocity of macroprojectile was measured at 520 meters per second with a 6% reduction in velocity at atmospheric pressure. A polyethylene film placed in the breech before firing contributed to a 12% increase in muzzle velocity. A 700 millimeters Hg level of vacuum was necessary for maximum number of transfornants. GUS expression was also detected in wheat leaf base tissue of microdissected shoot apices. High levels of transient gene expression were also observed in hard, compact embryogenic callus of rice. These results show that the airgun apparatus is a convenient, safe, and low-cost device for rapid transient gene expression studies in cereals.     

Circular dichroism of collagen, gelatin, and poly(proline) II in the vacuum ultraviolet.

Circular dichroism spectra for acid-soluble calfskin collagen, gelatin, and poly(proline) II in solution have been extended into the vacuum ultraviolet region. The extended spectrum of gelatin reveals that the circular dichroism of this unordered polymer is more closely related to the spectrum of charged polypeptides than might be evident from near ultraviolet work. A short-wavelength band is found at about 172 nm, which corresponds in position, magnitude, and sign to a band recorded earlier for poly(L -glutamic acid) at pH 8.0. This band is observed in a helical structure for the first time in the vacuum ultraviolet circular dichroism and absorption spectra of poly(proline) II. Both circular dichroism and absorption spectra point to the assignement of this band as the nσ*. Neither the nσ* nor the expected positive lobe of the ππ* helix band is observed in the extended circular dichroism spectrum of collagen. We postulate that these two bands cancel here in analogy to the case of α-helical poly(L -glutamic acid).     

A model of Agrobacterium tumefaciens vacuum infiltration into harvested leaf tissue and subsequent in planta transgene transient expression

Agrobacterium-mediated gene transfer, or agroinfiltration, can be a highly efficient method for transforming and inducing transient transgene expression in plant tissue. The technique uses the innate DNA secretion pathway of Agrobacterium tumefaciens to vector a particular plasmid-encoded segment of DNA from the bacteria to plant cells. Vacuum is often applied to plant tissue submerged in a suspension of A. tumefaciens to improve agroinfiltration. However, the effects of vacuum application on agroinfiltration and in planta transient transgene expression have not been well quantified. Here we show that vacuum application and release act to drive A. tumefaciens suspension into the interior of leaf tissue. Moreover, the amount of suspension that enters leaves can be predicted based on the vacuum intensity and duration. Furthermore, we show that transient expression levels of an agroinfiltrated reporter gene vary in response to the amount of A. tumefaciens vacuum infiltrated into leaf tissue, suggesting that vacuum infiltration conditions can be tailored to achieve optimal transient transgene expression levels after agroinfiltration.     

The insertion reactions of the p-complex silylenoid H<Subscript>2</Subscript>SiLiF with Si-X (X=F,Cl, Br,O, N) bonds

The insertion reactions of the silylenoid H₂SiLiF with SiH₃XH_n-1 (X = F, Cl, Br, O, N; n = 1, 1, 1, 2, 3) have been studied by DFT calculations. The results indicate that the insertions proceed in a concerted manner, forming H₃SiSiH₂XH_n-1 and LiF. The essence of H₂SiLiF insertion into Si-X bonds reactions are the donations of the electrons of X into the p orbital on the Si atom in H₂SiLiF and the σ electrons on the Si atom in H₂SiLiF to the positive SiH₃ group. The order of reactivity by H₂SiLiF insertion in vacuum indicates the reaction barriers decrease for the same-row element X from right to left and the same-family element X from up down in the periodic table. The insertion reactions in ether are similar to those in vacuum. The energy barriers in vacuum are higher than those in ether. The silylenoid insertions are thermodynamically exothermic both in vacuum and in ether.     

High-β island-divertor equilibria of a quasi-isodynamic stellarator

A stellarator vacuum field is found for which free-boundary MHD quasi-isodynamic equilibria with a nearly invariant island structure in the vacuum field region surrounding the plasma are obtained for 〈β〉 values up to about 0.07.     

Toward the mathematical modeling of heat and mass transfer in vacuum freeze-drying: I. Thermodynamic analysis of heat- and mass-transfer processes in capillary porous materials undergoing freeze-drying

A number of existing mathematical models of heat- and mass-transfer processes taking place inside a material undergoing vacuum freeze-drying are reviewed in brief. Some physical considerations with respect to freeze-drying in a vacuum are presented and a corresponding mathematical model is proposed to describe coupled heat and mass transfer inside the material undergoing freeze-drying. The model is based on linear nonequilibrium thermodynamic results. After appropriate numerical analysis, the model is expected to yield new data to be utilized in vacuum freeze-drying design and technology.     

Photochemical reactions in interstellar grains photolysis of co,NH3, and H2O

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH₃:H₂O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH₃ to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.     

Comparison of protein solution structures refined by molecular dynamics simulation in vacuum,with a generalized Born model,and with explicit water

The inclusion of explicit solvent water in molecular dynamics refinement of NMR structures ought to provide the most physically meaningful accounting for the effects of solvent on structure, but is computationally expensive. In order to evaluate the validity of commonly used vacuum refinements and of recently developed continuum solvent model methods, we have used three different methods to refine a set of NMR solution structures of a medium sized protein, Escherichia coliglutaredoxin 2, from starting structures calculated using the program DYANA. The three different refinement protocols used molecular dynamics simulated annealing with the program AMBER in vacuum (VAC), including a generalized Born (GB) solvent model, and a full calculation including explicit solvent water (WAT). The structures obtained using the three methods of refinements were very similar, a reflection of their generally well-determined nature. However, the structures refined with the generalized Born model were more similar to those from explicit water refinement than those refined in vacuum. Significant improvement was seen in the percentage of backbone dihedral angles in the most favored regions of , space and in hydrogen bond pattern for structures refined with the GB and WAT models, compared with the structures refined in vacuum. The explicit water calculation took an average of 200 h of CPU time per structure on an SGI cluster, compared to 15–90 h for the GB calculation (depending on the parameters used) and 2 h for the vacuum calculation. The generalized Born solvent model proved to be an excellent compromise between the vacuum and explicit water refinements, giving results comparable to those of the explicit water calculation. Some improvement for and angle distribution and hydrogen bond pattern can also be achieved by energy minimizing the vacuum structures with the GB model, which takes a much shorter time than MD simulations with the GB model.     

A.U and G.C base pairs in synthetic RNAS have characteristic vacuum UV CD bands.

The vacuum UV CD spectra of GpC, CpG, GpG, poly[r(A)], poly[r(C)], poly[r(U)], poly[r(A-U)], poly[r(G).r(C)], poly[r(A).r(U)], and poly[r(A-U).r(A-U)] were measured down to at least 174 nm. These spectra, together with the published spectra of poly[r(G-C).r(G-C)], CMP, and GMP, were sufficient to estimate the CD changes upon base pairing for four double-stranded RNAs. The vacuum UV CD bands of poly[r(A)], poly[r(C)], and the dinucleotides GpC and CpG were temperature dependent, suggesting that they were due to intrastrand base stacking. The dinucleotide sequence isomers GpC and CpG had very different vacuum UV CD bands, indicating that the sequence can play a role in the vacuum UV CD of single-stranded RNA. The vacuum UV CD bands of the double-stranded (G.C)-containing RNAs, poly[r(G).r(C)] and poly[r(G-C).r(G-C)], were larger than the measured or estimated vacuum UV CD bands of their constituent single-stranded RNAs and were similar in having an exceptionally large positive band at about 185 nm and negative bands near 176 and 209 nm. These similarities were enhanced in difference-CD spectra, obtained by subtracting the CD spectra of the single strands from the CD spectra of the corresponding double strands. The (A.U)-containing double-stranded RNAs poly[r(A).r(U)] and poly[r(A-U).r(A-U)] were similar only in that their vacuum UV CD spectra had a large positive band at 177 nm. The spectrum of poly[r(A).r(U)] had a shoulder at 188 nm and a negative band at 206 nm, whereas the spectrum of poly[r(A-U).r(A-U)] had a positive band at 201 nm. On the other hand, difference spectra of both of the (A.U)-containing polymers had positive bands at about 177 and 201 nm. Thus, the difference-CD spectra revealed CD bands characteristic of A.U and G.C base pairing. (ABSTRACT TRUNCATED AT 250 WORDS)     

Submergence-Induced Ethylene Synthesis,Entrapment, and Growth in Two Plant Species with Contrasting Flooding Resistances

Submergence-induced ethylene synthesis and entrapment were studied in two contrasting Rumex species, one flood-resistant (Rumex palustris) and the other flood-sensitive (Rumex acetosa). The application of a photoacoustic method to determine internal ethylene concentrations in submerged plants is discussed. A comparison with an older technique (vacuum extraction) is described. For the first time ethylene production before, during, and after submergence and the endogenous concentration during submergence were continuously measured on a single intact plant without physical perturbation. Both Rumex species were characterized by enhanced ethylene concentrations in the shoot after 24 h of submergence. This was not related to enhanced synthesis but to continued production and physical entrapment. In R. palustris, high endogenous ethylene levels correlated with enhanced petiole and lamina elongation. No dramatic change in leaf growth rate was observed in submerged R. acetosa shoots. After desubmergence both species showed an increase in ethylene production, the response being more pronounced in R. palustris. This increase was linked to the enhanced postsubmergence growth rate of leaves of R. palustris. Due to the very rapid escape of ethylene out of desubmerged plants to the atmosphere (90% disappeared within 1 min), substantial underestimation of internal ethylene concentrations can be expected using more conventional vacuum extraction techniques.