Kinetics of vesicle formation

 The kinetics of vesicle formation from a hydrotrope (sodium xylenesulfonate) solution of a surfactant (Laureth 4) is studied by the use of a stopped-flow apparatus combined with a dynamic light scattering device to determine vesicle size in the system. The hydrotrope system studied presents a system with a high surfactant solubilization combined with vesicle formation simply by dilution with water. The kinetic results show a single exponential decay time. The kinetic analysis indicates that the vesicles are formed from a molecular solution which resulted from the shear in the stopped-flow device and grow by monomeric association. Received: 1 October 1996 Accepted: 22 November 1996     

THE EFFECT OF 1,4-DIAZABICYCLO[2.2.2]OCTANE ON THE RADIOSENSITIVITY OF BACTERIA

Abstract— Hydroxyl radicals ('OH) are scavenged by 1,4-diazabicyclo[2.2.2]octane (DABCO) at a diffusion-controlled rate of 1.25 ± 0.1 × 10⁹ M ^-1s^-1. Unlike other efficient 'OH scavengers which exhibit protection of bacteria against irradiation both in oxic and hypoxic conditions, DABCO has been shown to protect Serratia marcescens and various strains of Escherichia coli only in oxic conditions.
DABCO appears to eliminate a component of the sensitization afforded by oxygen in all strains of E. coli tested. The level of this protection increases from ∼15% in the wild type AB 1157 to ∼100% in the recA uvrA mutant AB 2480. It is suggested that DABCO protects against lethal events that can occur on macromolecules other than DNA such as the cell membrane.
Results with added glycerol, as well as work in D₂O solution, indicate that DABCO is more likely to be acting by scavenging radicals rather than by quenching ¹O₂. If ¹O₂ is a component of the sensitization afforded by oxygen, then it is unlikely to be formed in a hydrophilic environment in the cell.     

1,3‐Dimethyl‐2‐oxo‐4,6‐diphenyl‐1,2,3,4‐tetrahydropyridine‐3‐carbonitrile

The crystal structure of the title compound, C₂₀H₁₈N₂O, reveals a distorted half‐chair conformation of the central tetra­hydro­pyridine (THP) ring, with the cyano‐ and adjacent phenyl‐substituted C atoms displaced by 0.329 (1) and ?0.315 (1) Å, respectively, from the THP best plane. Steric interactions force the phenyl rings out of the THP plane by 49.21 (9) and 65.76 (5)°. The cyano moiety is coplanar with the THP plane.     

Field evaluations of the VDmax approach for substantiation of a 25 kGy sterilization dose and its application to other preselected doses

The International and European standards for radiation sterilization require evidence of the effectiveness of a minimum sterilization dose of 25 kGy but do not provide detailed guidance on how this evidence can be generated. An approach, designated VD_max, has recently been described and computer evaluated to provide safe and unambiguous substantiation of a 25 kGy sterilization dose. The approach has been further developed into a practical method, which has been subjected to field evaluations at three manufacturing facilities which produce different types of medical devices. The three facilities each used a different overall evaluation strategy: Facility A used VD_max for quarterly dose audits; Facility B compared VD_max and Method 1 in side-by-side parallel experiments; and Facility C, a new facility at start-up, used VD_max for initial substantiation of 25 kGy and subsequent quarterly dose audits. A common element at all three facilities was the use of 10 product units for irradiation in the verification dose experiment.

The field evaluations of the VD_max method were successful at all three facilities; they included many different types of medical devices/product families with a wide range of average bioburden and sample item portion values used in the verification dose experiments. Overall, around 500 verification dose experiments were performed and no failures were observed. In the side-by-side parallel experiments, the outcomes of the VD_max experiments were consistent with the outcomes observed with Method 1.

The VD_max approach has been extended to sterilization doses >25 and <25 kGy; verification doses have been derived for sterilization doses of 15, 20, 30, and 35 kGy. Widespread application of the VD_max method for doses other than 25 kGy must await controlled field evaluations and the development of appropriate specifications/standards.     

Small-angle X-ray study of air-dried elastoidin using three- and one- dimensional correlation functions obtained from slit-smeared intensity

In the present paper an isotropic sample of air-dried elastoidin has been studied considering it to be a non-ideal two-phase densely packed system after the theories by Vonk [1]. The relevant important physical parameters obtained for the sample areE, the width of the transition layer,D, the average periodicity transverse to the layers, S/V, the specific inner surface ₁ and ₂, the volume fraction of two phases, i. e. matter and void,l ₁ andl ₂ the transversal lengths,l _r, the range of inhomogeneity,l _c, the length of coherence and 2E/D, the volume fraction of the transition layer. The values ofE obtained by two approches as given by Vonk [1] and Ruland [2] show but a small difference indicating the correctness of the analysis.     

Favorskii rearrangement of α,β-epoxy ketones

Reactions of α,β-epoxy ketones with nucleophilic bases generally take one of two courses: (1) α-displacement followed by β-elimination of water or (2) Favorskii rearrangement via a cyclopropanone or zwitterion intermediate. Among the factors that appear to control these reactions, it is suspected that an α′-substituent effect may operate. Such an effect has been confirmed by observing the conversion of 3,5,5,6 - tetramethyl - 2,3 - epoxycyclohexanone (1) to the ring-contracted γ-lactone 3, together with other Favorskii rearrangement products, on treatment with refluxing methanolic potassium hydroxide. The α′-methyl substituted steroid 2 under similar reaction conditions was transformed into roughly equal amounts of 4, 5 and 4 (all rationalized by a Favorskii-like mechanism). In each case the analogous epoxy ketone lacking an α′-Me substituent failed to give any Favorskii products.     

Complexes of divalent oxovanadium,manganese, iron,cobalt, nickel and copper with the ligand derived from the reaction of 2-aminopyridine and acetylacetone

Summary 2-Aminopyridine reacts with acetylacetone in the presence of VO^II, Mn^II, Fe^II, Co^II, Ni^II, and Cu^II metal salts to give complexes of the type [VO(Ap₂ac)₂X]X and [M(Ap₂ac)₂X₂] where (Ap₂ac) is the ligand formedin situ. The complexes are characterised as distorted octahedral by analyses, conductance, molecular weight, magnetic, electronic and i.r. spectral studies. The i.r. studies reveal that two molecules of aminopyridine are joined by a molecule of acetylacetone through a three carbon atom bridge and that the ligand coordinates through the azomethine and imino nitrogen atoms, whereas pyridine does not take part in coordination. The electronic spectra have been interpreted and tentative assignments are made. In the far i.r. spectra, various metal ligand vibrations are observed and discussed. Attempts to carry out electrophilic substitutions in the complexes failed.     

Emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile

The emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile is described. The effects of polymerization temperature, potassium persulfate initiator concentration, sodium lauryl sulfate emulsifier concentration on copolymer yield, molecular weight, and rate of copolymerization are described. The copolymer was found to have an azeotropic composition at 43 mole-% AMS. Reactivity ratios were determined to be 0.06 and 0.28 for AMS and MAN, respectively.     

Mass spectrometric methods for the analysis of chlorinated and nitrated isoflavonoids: a novel class of biological metabolites

Electrospray ionization combined with tandem mass spectrometry was applied to a study of some representative chlorinated and nitrated isoflavones-potential metabolites of isoflavones in inflammatory cells. Upon collision-induced dissociation of deprotonated [M - H](-) ions of these compounds, a number of structurally characteristic product ions were produced. The product ion analysis of 3'- and 8-chlorodaidzein in the tandom mass spectra led to ready differentiation of these isomers. 3-Nitro derivatives of both genistein and daidzein have product ions due to the losses of HNO(2) and two OH groups. Chlorinated derivatives of isoflavones were detected in cell-based experiments and their structures were proposed by comparing the tandem mass spectra of their product ions with those of standards. This work provides a suitable analytical basis to aid the characterization of chlorinated and nitrated metabolites in studies in vivo and in vitro.