Studies of inhibitor binding to the [4Fe-4S] cluster of quinolinate synthase

Stop for NadA! A [4Fe-4S] enzyme, NadA, catalyzes the formation of quinolinic acid in de?novo nicotinamide adenine dinucleotide (NAD) biosynthesis. A structural analogue of an intermediate, 4,5-dithiohydroxyphthalic acid (DTHPA), has an in?vivo NAD biosynthesis inhibiting activity in E. coli. The inhibitory effect can be explained by the coordination of DTHPA thiolate groups to a unique Fe site of the NadA [4Fe-4S] cluster.     

Micropatterning topology on soft substrates affects myoblast proliferation and differentiation

Micropatterning techniques and substrate engineering are becoming useful tools to investigate several aspects of cell-cell interaction biology. In this work, we rationally study how different micropatterning geometries can affect myoblast behavior in the early stage of in vitro myogenesis. Soft hydrogels with physiological elastic modulus (E = 15 kPa) were micropatterned in parallel lanes (100, 300, and 500 μm width) resulting in different local and global myoblast densities. Proliferation and differentiation into multinucleated myotubes were evaluated for murine and human myoblasts. Wider lanes showed a decrease in murine myoblast proliferation: (69 ± 8)% in 100 μm wide lanes compared to (39 ± 7)% in 500 μm lanes. Conversely, fusion index increased in wider lanes: from (46 ± 7)% to (66 ± 7)% for murine myoblasts, and from (15 ± 3)% to (36 ± 2)% for human primary myoblasts, using a patterning width of 100 and 500 μm, respectively. These results are consistent with both computational modeling data and conditioned medium experiments, which demonstrated that wider lanes favor the accumulation of endogenous secreted factors. Interestingly, human primary myoblast proliferation is not affected by patterning width, which may be because the high serum content of their culture medium overrides the effect of secreted factors. These data highlight the role of micropatterning in shaping the cellular niche through secreted factor accumulation, and are of paramount importance in rationally understanding myogenesis in vitro for the correct design of in vitro skeletal muscle models.     

Spontaneous grafting of diazonium salts: chemical mechanism on metallic surfaces

The spontaneous reaction of diazonium salts on various substrates has been widely employed since it consists of a simple immersion of the substrate in the diazonium salt solution. As electrochemical processes involving the same diazonium salts, the spontaneous grafting is assumed to give covalently poly(phenylene)-like bonded films. Resistance to solvents and to ultrasonication is commonly accepted as indirect proof of the existence of a covalent bond. However, the most relevant attempts to demonstrate a metal-C interface bond have been obtained by an XPS investigation of spontaneously grafted films on copper. Similarly, our experiments give evidence of such a bond in spontaneously grafted films on nickel substrates in acetonitrile. In the case of gold substrates, the formation of a spontaneous film was unexpected but reported in the literature in parallel to our observations. Even if no interfacial bond was observed, formation of the films was explained by grafting of aryl cations or radicals on the surface arising from dediazoniation, the film growing later by azo coupling, radical addition, or cationic addition on the grafted phenyl layer. Nevertheless, none of these mechanisms fits our experimental results showing the presence of an Au-N bond. In this work, we present a fine spectroscopic analysis of the coatings obtained on gold and nickel substrates that allow us to propose a chemical structure of such films, in particular, their interface with the substrates. After testing the most probable mechanisms, we have concluded in favor of the involvement of two complementary mechanisms which are the direct reaction of diazonium salts with the gold surface that accounts for the observed Au-N interfacial bonds as well as the formation of aryl cations able to graft on the substrate through Au-C linkages.     

Photodynamic activity of viral nanoparticles conjugated with C(60)

The development of viral nanoparticles (VNP) displaying multiple copies of the buckyball (C(60)) and their photodynamic activity is described. VNP-C(60) conjugates were assembled using click chemistry. Cell uptake and cell killing using white light therapy and a prostate cancer cell line is demonstrated.     

Antibacterial and antiparasitic effects of Bothropoides lutzi venom

The therapeutic potential of toxins has aroused great interest in the scientific community. Microbial resistance is a serious current public health problem, in part because of the wide use of antimicrobial drugs. Furthermore, there are several problems in the treatment of parasitic diseases such as leishmaniosis and Chagas' disease, including the low efficacy in some clinical phases of the diseases and the loss of effectiveness of benzonidazole in the chronic phase of Chagas' disease. In this context, the aim of this work was to study the antimicrobial and antiparasitic effects of Bothropoides lutzi total venom (BltTV). The venom exerted an antibacterial effect on S. aureus, with MIC=MLC=200 microg/mL. The inhibitory effects of BltTV on promastigote forms of Leishmania amazonensis and L. chagasi were assessed by counting of viable cells after incubation with BltTV. IC50 values of 234.6 microg/mL and 61.2 microg/mL, were obtained, respectively. Furthermore, the venom repressed epimastigote forms of Trypanosoma cruzi growth. Finally, BltTV was verified to affect murine peritoneal macrophages, causing a cytotoxic effect at the highest concentrations (100 and 50 microg/mL). In conclusion, Bothropoides lutzi venom demonstrated antibacterial and antiparasite effects, suggesting that the venom contains some substance(s) of therapeutic value.     

Codistances of 3-spherical buildings

We show that a 3-spherical building in which each rank 2 residue is connected far away from a chamber, and each rank 3 residue is simply 2-connected far away from a chamber, admits a twinning (i.e., is one half of a twin building) as soon as it admits a codistance, i.e., a twinning with a single chamber.     

Hybrid feedforward-feedback active noise reduction for hearing protection and communication

A hybrid active noise reduction (ANR) architecture is presented and validated for a circumaural earcup and a communication earplug. The hybrid system combines source-independent feedback ANR with a Lyapunov-tuned leaky LMS filter (LyLMS) improving gain stability margins over feedforward ANR alone. In flat plate testing, the earcup demonstrates an overall C-weighted total noise reduction of 40 dB and 30-32 dB, respectively, for 50-800 Hz sum-of-tones noise and for aircraft or helicopter cockpit noise, improving low frequency (<100 Hz) performance by up to 15 dB over either control component acting individually. For the earplug, a filtered-X implementation of the LyLMS accommodates its nonconstant cancellation path gain. A fast time-domain identification method provides a high-fidelity, computationally efficient, infinite impulse response cancellation path model, which is used for both the filtered-X implementation and communication feedthrough. Insertion loss measurements made with a manikin show overall C-weighted total noise reduction provided by the ANR earplug of 46-48 dB for sum-of-tones 80-2000 Hz and 40-41 dB from 63 to 3000 Hz for UH-60 helicopter noise, with negligible degradation in attenuation during speech communication. For both hearing protectors, a stability metric improves by a factor of 2 to several orders of magnitude through hybrid ANR.     

Cellular and antitumor activity of a new diethylene glycol benzoporphyrin derivative (lemuteporfin)

A newly synthesized diethylene glycol functionalized chlorin-type photosensitizer, lemuteporfin, was characterized for use in photodynamic therapy (PDT) in a panel of in vitro and in vivo test systems. The photosensitizer was highly potent, killing cells at low nanomolar concentrations upon exposure to activating light. The cellular uptake of lemuteporfin was rapid, with maximum levels reached within 20 min. Mitogen-activated lymphoid cells accumulated more of the lemuteporfin than their quiescent equivalents, supporting selectivity. Photosensitizer fluorescence in the skin increased rapidly within the first few minutes following intravenous administration to mice, then decreased over the next 24 h. Skin photosensitivity reactions indicated rapid clearance of the photosensitizer. Intravenous doses as low as 1.4 micromol/kg combined with exposure to 50 J/cm2 red light suppressed tumor growth in a mouse model. In conclusion, this new benzoporphyrin was found to be an effective photosensitizer, showing rapid uptake and clearance both in vitro and in vivo. This rapid photosensitization of tumors could be useful in therapies requiring a potent, rapidly accumulating photosensitizer, while minimizing the potential for skin photosensitivity reactions to sunlight following treatment.