Testing biological activity of model Maillard reaction products: studies on gastric smooth muscle tissues

Water-soluble Maillard reaction products obtained from five different model systems were investigated for their effects upon the mechanical activity of rat gastric smooth muscle. Most of the total Maillard reaction products applied at concentration of 1.5 mg/ml evoked contractions; among them the product obtained from arginine and glucose (Arg-Glc) produced the most powerful contractions. The product obtained from glycine and ascorbic acid (Gly-AsA) was the only one that brought about relaxation response. The high molecular weight fractions (>3,500 Da) isolated from the reaction systems Arg-Glc and Gly-AsA demonstrated effects similar in type and amplitude to those evoked by non-fractioned reaction products. The results obtained suggest that moieties of molecules acting upon the muscle tonus originate mainly from lysine and arginine residues; that these structures are available in both low and high molecular pools in similar concentrations, and most likely these fragments act upon membrane-located cellular structures involved in calcium transport.     

Protein-based hybrid catalysts--design and evolution

Artificial metalloenzymes result from the introduction of a catalytically competent non-native metal cofactor within a protein environment. In the present contribution, we summarize the recent achievements in the design and the optimization of such protein-based hybrid catalysts, with an emphasis on enantioselective transformations. The second part outlines the milestones required to achieve en masse production, screening and directed evolution of artificial metalloenzymes. In the spirit of Darwinian evolution, this will allow the full potential of such protein-based hybrid catalysts to be fully unraveled, thus complementing both homogeneous and enzymatic catalysis.     

On the observation of a gem diol intermediate after O–O bond cleavage by extradiol dioxygenases. A hybrid DFT study

Catalytic cycle intermediates of a representative extradiol dioxygenase, homoprotocatechuate 2,3-dioxygenase (HPCD), have recently been characterized in crystallo by Kovaleva and Lipscomb. The structures of the identified species indicate that the process of inserting oxygen into the catechol ring occurs stepwise, and involves an Fe(II)-alkylperoxo intermediate and its O–O cleavage product: a gem diol species. In general, these findings corroborate the results of our previous computational studies; however, the fact that the gem diol species is stable enough to be observed in the crystal form seems to be at odds with the computational mechanistic data, which suggest that this intermediate should very readily and spontaneously convert to the epoxide species. The key question then becomes what is actually observed in the X-ray experiments. Here we report additional computational studies undertaken with the hope of clarifying this issue. The results obtained for active site models hosting both the native and the alternative (4-sulfonylcatechol) substrate indicate that the stability of the gem diol species is substantially increased if an electron and a proton are added. If this occurs somehow, the lifetime of the intermediate should be sufficient to observe it.     

Epidemiology of a tick‐borne viral infection: theoretical insights and practical implications for public health

The morbidity of tick‐borne encephalitis (TBE) varies yearly by as much as 10‐fold among the people of Western Siberia. This long‐term variation is dependent on many factors such as the density of the tick populations, the prevalence of TBE virus (TBEV) among sub‐adult ticks, the yearly virulence of the TBEV, and prophylactic measures. Here we highlight the role of small mammal hosts in the circulation of TBEV through the ecosystem. Refining classical models of non‐viremic horizontal transmission, we emphasize the recently understood fact that the physiological and immunological status of the small mammal hosts affects the tick and virus‐host interactions. In addition to its theoretical interest, our approach may lead to some practical improvements in the precision of epidemiological forecasts and perhaps in forestalling the severity of outbreaks of TBE, or, at least, in forewarning medical authorities and the general public of impending TBE outbreaks.     

Activity-guided isolation of antiplasmodial dihydrochalcones and flavanones from Piper hostmannianum var. berbicense

The bioassay-guided purification of an n-hexane extract from the leaves of Piper hostmannianum var. berbicense led to the isolation of four monoterpene or prenyl-substituted dihydrochalcones (1a, 1b, 2, 3) as well as the known compounds 2',6'-dihydroxy-4'-methoxydihydrochalcone (4), linderatone (5), strobopinin (6), adunctin E (7) and (-)-methyllinderatin (8). Their structures were established on the basis of NMR and X-ray analysis. (-)-Methyllinderatin, linderatone and 2',6'-dihydroxy-4'-methoxydihydrochalcone exhibited the most potent antiplasmodial activity with IC50 values of 5.64, 10.33 and 12.69 microM, respectively against both chloroquine-sensitive and resistant strains of Plasmodium falciparum (F32,FcB1). The activity of (-)-methyllinderatin was confirmed in vivo against Plasmodium vinckei petteri in mice (80% of reduction of parasitemia) at a dose of 20 mg/kg/day.     

Neuro-immune interactions via the cholinergic anti-inflammatory pathway

The overproduction of TNF and other cytokines is associated with the pathophysiology of numerous diseases. Controlling cytokine synthesis and release is critical for preventing unrestrained inflammation and maintaining health. Recent studies identified an efferent vagus nerve-based mechanism termed "the cholinergic anti-inflammatory pathway" that controls cytokine production and inflammation. Here we review current advances related to the role of this pathway in neuro-immune interactions that prevent excessive inflammation. Experimental evidence indicates that vagus nerve cholinergic anti-inflammatory signaling requires alpha7 nicotinic acetylcholine receptors expressed on non-neuronal cytokine-producing cells. Alpha7 nicotinic acetylcholine receptor agonists inhibit cytokine release and protect animals in a variety of experimental lethal inflammatory models. Knowledge related to the cholinergic anti-inflammatory pathway can be exploited in therapeutic approaches directed towards counteracting abnormal chronic and hyper-activated inflammatory responses.     

Covalent bonding of vancomycin to Ti6Al4V alloy pins provides long-term inhibition of Staphylococcus aureus colonization

Self-protecting Ti6Al4V alloy pins were prepared by covalent bonding of bis(ethylene glycol) linkers, then vancomycin to the oxidized, aminopropylated Ti6Al4V alloy surface. Fluorescence modification-enabled estimation of yields of free amines on the metallic surface monolayer at each reaction step. The vancomycin-protected Ti6Al4V pins were not colonized by Staphylococcus aureus, even after 44days storage in physiological buffer. These results provide a basis for testing self-protection against S. aureus colonization in animal models.     

New syntheses of tetrazolylmethylphenylalanine and O-malonyltyrosine as pTyr mimetics for the design of STAT3 dimerization inhibitors

Investigation within the pTyr-binding pocket of the STAT3 SH2 domain led us to develop a novel synthesis of two pTyr mimetics, l-tetrazolylmethylphenylalanine (l-Tmp) and l-O-malonyltyrosine (l-OMT), that were next incorporated in a high affinity ligand of STAT3 SH2 domain. Biological evaluation of peptidomimetics on STAT3 dimerization identified l-OMT as the first non-phosphorus pTyr mimetic so far reported against STAT3 SH2 domain, harboring an activity similar to that of the Pmp-containing reference peptidomimetic.     

UmuD and RecA directly modulate the mutagenic potential of the Y family DNA polymerase DinB

DinB is the only translesion Y family DNA polymerase conserved among bacteria, archaea, and eukaryotes. DinB and its orthologs possess a specialized lesion bypass function but also display potentially deleterious -1 frameshift mutagenic phenotypes when overproduced. We show that the DNA damage-inducible proteins UmuD(2) and RecA act in concert to modulate this mutagenic activity. Structural modeling suggests that the relatively open active site of DinB is enclosed by interaction with these proteins, thereby preventing the template bulging responsible for -1 frameshift mutagenesis. Intriguingly, residues that define the UmuD(2)-interacting surface on DinB statistically covary throughout evolution, suggesting a driving force for the maintenance of a regulatory protein-protein interaction at this site. Together, these observations indicate that proteins like RecA and UmuD(2) may be responsible for managing the mutagenic potential of DinB orthologs throughout evolution.     

Blood schizontocidal activity of methylene blue in combination with antimalarials against Plasmodium falciparum

Methylene blue (MB) is the oldest synthetic antimalarial. It is not used anymore as antimalarial but should be reconsidered. For this purpose we have measured its impact on both chloroquine sensitive and resistant Plasmodium strains. We showed that around 5 nM of MB were able to inhibit 50% of the parasite growth in vitro and that late rings and early trophozoites were the most sensitive stages; while early rings, late trophozoites and schizonts were less sensitive. Drug interaction study following fractional inhibitory concentrations (FIC) method showed antagonism with amodiaquine, atovaquone, doxycycline, pyrimethamine; additivity with artemether, chloroquine, mefloquine, primaquine and synergy with quinine. These results confirmed the interest of MB that could be integrated in a new low cost antimalarial combination therapy.