Continuous epoxidation of soybean oil: operational analysis and process development

Continuous epoxidation of soybean oil: operational analysis and process development The epoxidation of refined soybean oil with peracetic acid is examined having special regard to the mass and heat transfer phenomena as well as to distribution coefficients depending on conversion and temperature. The process is described by a mathematic mechanistic model based on the cooled continuously stirred two-phase tank reactor. The process is limited by hydrodynamics and chemical kinetics. The main operation parameters feed temperature of coolant, volumetric rate of the lipoid phase, and residence time are optimized with respect to the space-time-yield. The two-stage countercurrent cascade of tank reactors leads to higher space-time-yields as well as higher epoxide yields.     

Sequence Analysis of 203 Kilobases from Saccharomyces cerevisiae Chromosome VII

The nucleotide sequences of five major regions from chromosome VII of Saccharomyces cerevisiae have been determined and analysed. These regions represent 203 kilobases corresponding to approximately one-fifth of the complete yeast chromosome VII. Two fragments originate from the left arm of this chromosome. The first one of about 15·8 kb starts approximately 75 kb from the left telomere and is bordered by the SKI8 chromosomal marker. The second fragment covers the 72·6 kb region between the chromosomal markers CYH2 and ALG2. On the right chromosomal arm three regions, a 70·6 kb region between the MSB2 and the KSS1 chromosomal markers and two smaller regions dominated by the KRE11 marker and another one in the vicinity of the SER2 marker were sequenced. We found a total of 114 open reading frames (ORFs), 13 of which were completely overlapping with larger ORFs running in the opposite direction. A total of 44 yeast genes, the physiological functions of which are known, could be precisely mapped on this chromosome. Of the remaining 57 ORFs, 26 shared sequence homologies with known genes, among which were 13 other S. cerevisiae genes and five genes from other organisms. No homology with any sequence in the databases could be found for 31 ORFs. Furthermore, five Ty elements were found, one of which may not be functional due to a frame shift in its Ty1B amino acid sequence. The five chromosomal regions harboured five potential ARS elements and one sigma element together with eight tRNA genes and two snRNAs, one of which is encoded by an intron of a protein-coding gene. © 1997 by John Wiley & Sons, Ltd.     

Development and immunobiological evaluation of nanoparticles containing an immunodominant epitope of herpes simplex virus

Herpes simplex virus (HSV) 1 and 2 are viruses that infect individuals worldwide and for which there is no cure or vaccine available. The protective response against herpes is mostly mediated by CD8 T lymphocytes that respond to the immunodominant SSIEFARL epitope. However, there are some obstacles concerning the use of free SSIEFARL for vaccine or immunotherapy. The aim of this study was to evaluate the feasibility of nanoencapsulation of SSIEFARL and its immunostimulatory properties. Nano/SSIEFARL was produced by interfacial polymerization in methylmetacrylate, and the physico‐chemical properties, morphology and immunobiological parameters were evaluated. To evaluate the ex vivo capacity of Nano/SSIEFARL, we used splenocytes from HSV‐1‐infected mice to enhance the frequency of SSIEFARL‐specific CD8 T lymphocytes. The results indicate that Nano/SSIEFARL has a spherical shape, an average diameter of 352 ± 22 nm, the PDI was 0.361 ± 0.009 and is negatively charged (−26.30 ± 35). The stability at 4°C was 28 days. Also, Nano/SSIEFARL is not toxic for cells at low concentrations in vitro and it is taken up by JAWS II dendritic cells. No histopathological changes were observed in kidneys, liver and lymph nodes of animals treated with Nano/SSIEFARL. Nan/SSIEFARL increased the production of IL‐1β, TNF‐α and IL‐12 by the dendritic cells. Finally, Nano/SSIEFARL expanded the frequency of SSIEFARL‐specific CD8+T lymphocytes at the same rate as free SSIEFARL. In conclusion all data together indicate that SSIEFARL is suitable for nanoencapsulation, and the system produced presents some immunoadjuvant properties that can be used to improve the immune response against herpes.     

High conversion study of “living” radical polymerization of styrene using DSC

The influence of temperature on nitroxide-controlled living radical polymerization of styrene was examined. It has been established that only in a temperature range of 110°C to 150°C nitroxides are able to control radical polymerization. At temperatures above 160°C the reaction was of rather a free radical character. The results were similar for all the various nitroxides used as capping agents: TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), 4-hydroxy-TEMPO, 4-oxo-TEMPO and 4-acetamido-TEMPO. Differences were found only in the induction times of polymerization and were probably due to side reactions with the initiator (benzoyl peroxide). Living radical polymerization can be best controlled with these nitroxides at temperatures between 120°C and 140°C.     

Mouse pregnancy-specific glycoproteins: tissue-specific expression and evidence of association with maternal vasculature

The pregnancy-specific glycoproteins (Psg) are secreted hormones encoded by multiple genes in rodents and primates, and are thought to act as immune modulators. The only Psg receptor identified is CD9, through which Psg17 induces cytokine production from macrophages cultured in vitro. We examined temporal and spatial aspects of Psg and CD9 expression during mouse pregnancy to determine whether their expression patterns support a role in immune modulation. Using in situ hybridisation, immunohistochemistry and RT-PCR we found Psg expression in trophoblast giant cells and in the spongiotrophoblast. Psg22 is the predominant Psg family member expressed in giant cells. Detectable Psg is associated predominantly with endothelial cells lining vascular channels in the decidua, rather than with maternal immune cell markers. CD9 expression exhibited partial overlap with Psg, but without exclusive co-localisation. CD9 was observed in decidual cells surrounding early implantation sites, and in the endometrium. However, embryo transfer of wild-type embryos to CD9-deficient females indicates that maternal CD9 is not essential for successful pregnancy.     

Size-dependent absolute quantum yields for size-separated colloidally-stable silicon nanocrystals

Size-selective precipitation was used to successfully separate colloidally stable allylbenzene-capped silicon nanocrystals into several visible emitting monodisperse fractions traversing the quantum size effect range of 1-5 nm. This enabled the measurement of the absolute quantum yield and lifetime of photoluminescence of allylbenzene-capped silicon nanocrystals as a function of size. The absolute quantum yield and lifetime are found to monotonically decrease with decreasing nanocrystal size, which implies that nonradiative vibrational and surface defect effects overwhelm spatial confinement effects that favor radiative relaxation. Visible emission absolute quantum yields as high as 43% speak well for the development of "green" silicon nanocrystal color-tunable light emitting diodes that can potentially match the performance of their toxic heavy metal chalcogenide counterparts.     

Crystallite sizes and lattice parameters of nano-biomagnetite particles

Average crystallite sizes of microbially synthesized pure, metal-, and lanthanide-substituted magnetite (bio-magnetite) were determined for a variety of incubation times and temperatures, substitutional elements and amounts, bacterial species, and precursor types. The intriguing difference between nanoparticle bio-magnetite and chemically synthesized magnetite (chem-magnetite) was that powder X-ray diffraction (XRD) data showed that the bio-magnetite exhibited slightly smaller lattice parameters, however, Raman Spectroscopy exhibited no difference in Fe-O bonding. These results indicate that bio-magnetite likely exhibits a more compact crystal structure with less uncoordinated iron on the surface suppressing negative pressure effects. The bio-magnetite with decreased lattice parameters could have potential technological advantages over current commercial chemically synthesized magnetites.