Application of the bacteriophage Mu-driven system for the integration/amplification of target genes in the chromosomes of engineered Gram-negative bacteria—mini review

The advantages of phage Mu transposition-based systems for the chromosomal editing of plasmid-less strains are reviewed. The cis and trans requirements for Mu phage-mediated transposition, which include the L/R ends of the Mu DNA, the transposition factors MuA and MuB, and the cis/trans functioning of the E element as an enhancer, are presented. Mini-Mu(LR)/(LER) units are Mu derivatives that lack most of the Mu genes but contain the L/R ends or a properly arranged E element in cis to the L/R ends. The dual-component system, which consists of an integrative plasmid with a mini-Mu and an easily eliminated helper plasmid encoding inducible transposition factors, is described in detail as a tool for the integration/amplification of recombinant DNAs. This chromosomal editing method is based on replicative transposition through the formation of a cointegrate that can be resolved in a recombination-dependent manner. (E-plus)- or (E-minus)-helpers that differ in the presence of the trans-acting E element are used to achieve the proper mini-Mu transposition intensity. The systems that have been developed for the construction of stably maintained mini-Mu multi-integrant strains of Escherichia coli and Methylophilus methylotrophus are described. A novel integration/amplification/fixation strategy is proposed for consecutive independent replicative transpositions of different mini-Mu(LER) units with “excisable” E elements in methylotrophic cells

Neutrophil Paralysis in Plasmodium vivax Malaria

Plasmodium vivax is responsible for approximately 60–80% of the malaria cases in the world, and contributes to significant social and economic instability in the developing countries of Latin America and Asia. The pathogenesis of P. vivax malaria is a consequence of host derived inflammatory mediators. Hence, a better understanding of the mechanisms involved in induction of systemic inflammation during P. vivax malaria is critical for the clinical management and prevention of severe disease. The innate immune receptors recognize Plasmodium sp. and initiate a broad spectrum of host defense mechanisms that mediate resistance to infection. However, the innate immune response is the classic “two-edged sword”, and clinical malaria is associated with high levels of circulating pro-inflammatory cytokines. Our findings show that both monocytes and neutrophils are highly activated during malaria. Monocytes produced high levels of IL-1β, IL-6 and TNF-α during acute malaria. On the other hand, neutrophils were a poor source of cytokines, but displayed an enhanced phagocytic activity and superoxide production. Unexpectedly, we noticed an impaired chemotaxis of neutrophils towards an IL-8 (CXCL8) gradient. We proposed that neutrophil paralysis is in part responsible for the enhanced susceptibility to bacterial infection observed in malaria patients

Photophysical and photochemical properties of a water-soluble perylene diimide derivative

WOS: 000089411700003The absorbance maximum of synthesized water soluble perylene 4-carboxylphenyl-bis-diimide (PECA) is found to be about 50 nm lower in water, as compared to absorbance in organic solvents, and the singlet energy is 61.4 kcal mol(-1) in aqueous solutions, compared to 54.4 kcal mol(-1) in organic solvents. The fluorescence quantum yields were similar in both media but radiative and fluorescence lifetimes are found to be enhanced about twice (tau(f) from 8 to 15 ns), and the rate of fluorescence is decreased twofold in aqueous solution, as compared to organic solutions. PECA is proven to produce reactive superoxide anion and/or hydroperoxy radical in aqueous solutions, in the pH range of 6-12 (phi(O2 .-)(PECA) = 0.062 at pH=9). The superoxide/hydroperoxy formation is found to be enhanced in the presence of ferric ions (phi(O2 .-)(PECA) = 0.10 at pH=9). The quantum yield of flouresence emmission, Q(f), was measured to be 1.00 at pH 11.85, and 0.87 at pH 6.60. The difference is attributed to an aggregation effect due to low solubility in neutral aqueous solution. Fluorescence quenching by Co+2 ions has yielded a quenching rate of 2.3 x 10(12) M-1 s(-1) for perylene diimide. The degradation of bromacil and 2,4-dichlorophenoxyacetic acid (2,4-D) pesticides in neutral aqueous solutions has proven that PECA/Fe+3 solar photocatalyst is as reactive as singlet oxygen in photo oxidations for organic pollutants. High thermal and photo stabilities and the regain of catalysts on precipitation, are the advantages with respect to classical triplet organic photosensitizers (methylene blue, rose bengal, etc.) employed for singlet oxygen photodegradations. (C) 2000 Elsevier Science S.A. All rights reserved

Structure and luminescent properties of the 4-arylidene-2-aryl-5-oxazolones(azlactones) in solution and crystalline state

WOS: 000081908900005Experimental and theoretical evaluations have proven that very low fluorescence quantum yields of azlactones in solution are not caused by an efficient inter system crossing from S-1*(pi pi) to T*(n pi) states, but rather from solvation and steric effects, that result in non-planarity of the molecular system. High fluorescence quantum yields in the solid state are attributed to the planarity of the azlactone molecule upon packing into the crystal lattice. Supporting evidence was found upon observation of the excited state proton transfer (ESIPT) bands of fluorescence emissions of o-hydroxyarylidene derivatives. The photoinstability of azlactones in liquid states are attributed to photochemical E-Z isomerization and cleavage of the hetero ring alpha to the carbonyl group

Photoinduced energy-electron transfer studies with naphthalene diimides

WOS: 000088293700002Seven derivatives of naphthalene diimides, synthesized, have shown similar photophysical properties. Low fluorescence quantum yields (0.002-0.006) and short fluorescence lifetimes (5-18 ps) have suggested rapid intersystem crossing processes from excited singlet state. Quenching of fluorescence emissions of aromatic donor molecules, i.e. naphthalene, phenanthrene and pyrene, at rates reaching to diffusion Limits in acetonitrile (2-8 x 10(10) M-1 s(-1)), have proven the electron acceptor capacities of naphthalene diimides. Photooxydation of styrene to benzaldehyde, in presence of naphthalene diimide (NDI) molecule, is found to occur at similar rates with respect to perylene diimides. Addition of ferric and cupric ions to NDI, have enhanced the formation rate of benzaldehyde by about two-fold. Photooxidation of alpha-terpinene with naphthalene diimide, produced only p-cymene, no endoperoxide adduct was identified. Naphthalene diimides appear to produce no singlet oxygen, and photooxidation probably occurs on radical chain reactions of super oxide anion radical. But the electron transfer electron via excited triplet or singlet state, remains to be unclear. (C) 2000 Elsevier Science S.A. All rights reserved

New chiral E- and Z-isomers of the 1R,4R-2-arylidene-p-menthane-3-ones in induced cholesteric and ferroelectric liquid crystals

A novel pair of the E- and Z-isomeric 1R,4R-2-(4-heptyloxyphenyl)-benzylidene-p-menthan-3-ones has been prepared and the influence of distinctions in their molecular geometry on macroscopic properties of liquid crystal systems with the induced supra-molecular helical structure has been studied. The significantly lower helical twisting power of the chiral Z-isomer in comparison with that of E- one has been confirmed in the case of induced cholesteric systems based on 4-pentyl-4-cyanobiphenyl. The phase behavior and ferroelectric characteristics have been investigated for smectic-C* compositions based on the eutectic mixture of the homological 4-hexyloxyphenyl-4'-hexyloxy- and 4-hexyloxyphenyl-4'-octyloxybenzoates containing the novel isomeric chiral dopants. The spontaneous polarisation of the opposite signs induced by the isomeric chiral components has been revealed for the compositions studied. Distinctions in phase states, absolute values of the spontaneous polarization, smectic tilt angle and rotation viscosity of the systems obtained are discussed

High fluorescence emissions of some natural benzofurane derivatives isolated from Styrax officinalis

WOS: 000088382300011The fluorescent properties of several natural benzofuran derivatives, egonols, isolated from Styrax officinalis, were determined. The studied egonol derivatives were found to be effective UV organic luminophores, with quantum yields of near to unity, phi(f) = 0.92. The fluorescence quenching experiments with electron donor molecules of aniline, N,N-dimethylaniline and carbazolocarbazole, presented very high efficiency of quenching at above diffusion quenching rates of 4.5x10(10), 2.1x10(x) and 5.6x10(12) s(-1)mol(-1), respectively. A strong electron acceptor molecule, tetranitrofluorenone, presented quenching rate of 2.6x10(11) s(-1)mol(-1). It is concluded that the first excited singlet state of egonol molecule is a more efficient electron acceptor