Application of mixtures of tartaric acid derivatives in resolution via supercritical fluid extraction

Racemic N-methylamphetamine (rac-MA) was resolved with 2R,3R-tartaric acid (TA) and its derivatives (O,O'-dibenzoyl-(2R,3R)-tartaric acid monohydrate (DBTA) and O,O'-di-p-toluoyl-(2R,3R)-tartaric acid (DPTTA)), individually and using them in different combinations. After partial diastereomeric salt formation, the free enantiomers were extracted by supercritical fluid extraction using carbon dioxide as solvent. DBTA and DPTTA are efficient resolving agents for rac-MA, the best chiral separation being obtained at a molar ratio of 0.25 resolving agent to racemic compound for both resolving agents (ee(E) = 82.5% and ee(E) = 57.9%, respectively). Compared with the two other acids, TA is practically unsuitable for enantiomer separation (ee(E) < 5%). Applying a mixture of one individually active and one ineffective acid in half the equivalent molar ratio, when the acids are in 1:1 ratio in the mixture, the resolution efficiency values obtained exceeded those obtained by using the components individually. Decreasing the molar ratio of resolving agent mixture to 0.25, at which the individual resolving agents give the best chiral separation, the obtained resolution efficiency values did not differ significantly from those expected. The outcome of the resolution process depended only on the amount of the individually active resolving agents in the mixture.     

Preparation of magnetic resonance contrast agents activated by beta-galactosidase

The preparation of beta-EgadMe and alpha-EgadMe, magnetic resonance (MR) contrast agents that can be used for in vivo detection of beta-galactosidase, is described. Diastereomerically pure beta-EgadMe can be synthesized by kinetically resolving the starting material as described in Step 1. The total time for the preparation of the racemic mixture of beta-EgadMe is about 8 d, and the total time for an diastereomerically resolved agent is about 9 d. The final metallated agent is stable at room temperature as a solid or in aqueous buffer (pH 5.5-10) indefinitely. Diastereomerically pure alpha-EgadMe can be prepared by beginning the synthesis with enantiomerically pure bromopropionic acid. The total time for the preparation of racemic alpha-EgadMe or diastereomerically pure alpha-EgadMe is about 8 d. The final metallated agent is stable at room temperature as a solid or in aqueous buffer (pH 5.5-10) indefinitely.     

Selecting Resolving Agents with Respect to Their Eutectic Compositions

In order to develop a resolution procedure for a given racemic compound, the first and the most important step is finding the most suitable resolving agent. We studied 18 individual resolutions that were carried out with resolving agents having high eutectic composition. We found that very high enantiomeric excess values were obtained in all cases. We assume that the eutectic composition of a given resolving agent is one of the most important properties that should always be considered during the search for the most efficient resolving agent. Chirality 28:230–234, 2016. © 2016 Wiley Periodicals, Inc.     

A general criterion for molecular recognition: implications for chiral interactions

A general criterion is formulated for molecular recognition. The criterion for recognition is the inequality of the distance matrices of complexes of different compounds with a resolving agent under ambient experimental conditions. It is shown how this criterion provides for an objective, well-defined, and simple explanation for recognition of chiral compounds. This approach may be used to explain models (e.g., three-point of attachment) and relationships for chiral recognition. It is also shown how one-, two-, or three-point mechanisms are equivalent in this formalism and could result in chiral recognition. Examples are used to illustrate how the so called one- or two-point mechanisms may be operative in many experimental findings. Symmetry requirements of resolving agents may also be derived from considerations of distance matrices. Finally, the reciprocal relationship of chiral resolving agents is easily derived from the present method of analysis.     

Effect of mixed macromolecular crowding agents on protein folding

In cells, proteins fold and unfold in the presence of macromolecules with various sizes and shapes. Recent experiments by Liang and coworkers (J Biol Chem 2004;279:55109-55116; J Mol Biol 2006;364:469-482) show that protein refolding is enhanced by a mixture of two different crowding agents relative to the individual crowding agents and an optimal mixing ratio exists. Here, we present a theory that predicts the existence of an optimal mixing ratio. The theory is based on models for calculating the changes in the chemical potentials of the folded and unfolded states by a mixture of crowders. The existence of an optimal mixing ratio results from the dependences of these chemical-potential changes on crowder sizes and concentrations, which can be argued to be quite general. We further predict that, for any crowding agent, the stabilizing effect can be optimized both by varying the molecular weight and the mixing ratio of two species with different molecular weights.     

Synergistic effect of arachidonic acid and cyclic AMP on glucose transport in 3T3-L1 adipocytes

The combined effect of arachidonic acid and cAMP on glucose transport was examined in 3T3-L1 adipocytes. In cells pre-treated with arachidonic acid and increasing concentrations of 8-bromo cAMP for 8 h, although either agent alone enhanced glucose uptake, the simultaneous presence of both agents dramatically increased 2-deoxyglucose uptake in a synergistic fashion. Insulin-stimulated glucose transport, on the other hand, was only slightly affected. The synergistic effect of these two agents was abolished in the presence of cycloheximide. Immunoblot analysis revealed that the contents of ubiquitous glucose transporter (GLUT1) in total cellular and plasma membranes were similarly augmented in cells pre-treated with both arachidonic acid and 8-bromo cAMP, to a greater extent than the additive effect of each agent alone. The content of GLUT4, on the other hand, was not altered under the same experimental conditions. In cells pre-treated with 4beta-phorbol 12beta-myristate 13alpha-acetate (PMA) for 24 h to down-regulate protein kinase C (PKC), the subsequent synergistic effect of arachidonic acid and 8-bromo cAMP was greatly inhibited. In addition, pre-treatment with both PMA and 8-bromo cAMP enhanced glucose transport in a similarly synergistic fashion. Thus the present study seems to indicate that arachidonic acid may act with cAMP in a synergistic way to increase glucose transport by a PKC-dependent mechanism. The increased activity may be accounted for by increased GLUT1 synthesis.     

Assessment of the effect of biosurfactant produced by Pseudomonas aeruginosa in lethality of Bacillus thuringiensis Berl. against 3rd instars larvae of white cabbage butterfly (Pieris brassicae L.)

Surfactant that is produced from cheap sources like oil sludge by biological agents such as bacteria can be used in various industrial processes. For example, it can be used in environmental processes such as bioremediation and elimination of environmental pollutants, and acts as synergistic agents and distributor pesticides on waxy leaves in agriculture. In this study, biosurfactant which is produced by Pseudomonas aeruginosa (isolated from petroleum sludge) at the intervals of 24, 48, 72 and 96?h, along with chemical surfactant Tween 80 and the biological control agent, Bacillus thuringiensis, in a pilot project for controlling one important cabbage pest (Pieris brassicae), their synergistic properties were evaluated. Statistical analysis of the results showed that B. thuringiensis in combination with biosurfactant produced at different times and B. thuringiensis in combination with chemical surfactant Tween 80 when compared with control treatments like B. thuringiensis alone and B. thuringiensis plus tween 80 as positive controls and distilled water as negative control have significant differences (p?<?0.05). This research showed that surfactant treatment produced at the intervals of 24 and 48?h in combination with B. thuringiensis has the greatest synergistic effect when compared to chemical surfactant treatment. This study concluded that biosurfactant can be used as a distributor and synergistic agent against plant pests and in addition to this, their biological roles in bioremediation can be used as a viable alternative to non-economical chemical surfactants that annually enter millions of tonnes of harmful chemical substances into the fields and underground water.     

The combination of BH3-mimetic ABT-737 with the alkylating agent temozolomide induces strong synergistic killing of melanoma cells independent of p53

Metastatic melanoma has poor prognosis and is refractory to most conventional chemotherapies. The alkylating agent temozolomide (TMZ) is commonly used in treating melanoma but has a disappointing response rate. Agents that can act cooperatively with TMZ and improve its efficacy are thus highly sought after. The BH3 mimetic ABT-737, which can induce apoptosis by targeting pro-survival Bcl-2 family members, has been found to enhance the efficacy of many conventional chemotherapeutic agents in multiple cancers. We found that combining TMZ and ABT-737 induced strong synergistic apoptosis in multiple human melanoma cell lines. When the drugs were used in combination in a mouse xenograft model, they drastically reduced tumor growth at concentrations where each individual drug had no significant effect. We found that TMZ treatment elevated p53 levels, and that the pro-apoptotic protein Noxa was elevated in TMZ/ABT-737 treated cells. Experiments with shRNA demonstrated that the synergistic effect of TMZ and ABT-737 was largely dependent on Noxa. Experiments with nutlin-3, a p53 inducer, demonstrated that p53 induction was sufficient for synergistic cell death with ABT-737 in a Noxa-dependent fashion. However, p53 was not necessary for TMZ/ABT-737 synergy as demonstrated by a p53-null line, indicating that TMZ and ABT-737 together induce Noxa in a p53-independent fashion. These results demonstrate that targeting anti-apoptotic Bcl-2 members is a promising method for treating metastatic melanoma, and that clinical trials with TMZ and Bcl-2 inhibitors are warranted.     

Chiral nuclear magnetic resonance shift reagents: Lanthanide mixtures with 1-(1-naphthyl) ethylurea derivatives of amino acids

Esters of 1-(1-naphthly)ethylurea derivatives of L-valine, L-leucine, L-tert-leucine, and L-proline are examined as organic-soluble chiral nuclear magnetic resonance (NMR) resolving agents. The reagents are useful for resolving the spectra of chiral sulfoxides, amines, alcohols, and carboxylic acids. Enantiomeric resolution is caused by a combination of diastereomeric effects and the different association constants of the substrates with the resolving agents. Organic-soluble lanthanide species are added to resolving agent-substrate mixtures and often enhance the enantiomeric resolution. The enhancement occurs because the substrate that exhibits weaker binding with the resolving agent is more available to bond to the lanthanide. Broadening in the spectra with lanthanides is reduced at 50°C. Enantiomeric resolution is still observed at elevated temperatures. Chirality 9:1–9, 1997. © 1997 Wiley-Liss, Inc.     

Enantioseparation of secondary alcohols by diastereoisomeric salt formation

A general method was found for the resolution of the racemic 1-phenyl-1-propanol (1) and 1-phenyl-2-propanol (2) with various resolving agents. Monoesters of the alcohols were prepared, which were then reacted with different chiral bases. Successful optical resolutions were achieved only with the maleic acid monoesters (3 and 6). Alcohol 1 has been resolved to >99% enantiomeric excess by diastereoisomeric salt formation via its maleic acid monoester (3) using cinchonidine (9) as resolving agent. Alcohol 2 has been obtained in 98% enantiomeric excess by diastereoisomeric salt formation via its the maleic acid monoester (6) using (+)-dehydroabietylamine (11) as resolving agent.     

Optimizing combination chemotherapy by controlling drug ratios

Cancer chemotherapy treatments typically employ drug combinations in which the dose of each agent is pushed to the brink of unacceptable toxicity; however, emerging evidence indicates that this approach may not be providing optimal efficacy due to the manner in which drugs interact. Specifically, whereas certain ratios of combined drugs can be synergistic, other ratios of the same agents may be antagonistic, implying that the most efficacious combinations may be those that utilize certain agents at reduced doses. Advances in nano-scale drug delivery vehicles now enable the translation of in vitro information on synergistic drug ratios into improved anticancer combination therapies in which the desired drug ratio can be controlled and maintained following administration in vivo, so that synergistic effects can be exploited. This "ratiometric" approach to combination chemotherapy opens new opportunities to enhance the effectiveness of existing and future treatment regimens across a spectrum of human diseases.     

Enhanced efficiency due to the use of achiral additives in the optical resolution of 1-phenylethylamine by its glutaric acid derivative

Racemic 1-phenylethylamine was optically resolved by its own derivative formed with glutaric acid namely (+)-(R)-N-(1-phenylethyl)glutaramic acid. The amide acid resolving agent was synthesized from (+)-(R)-1-phenylethylamine by N-derivatization. The glutaric acid derivative was the next in a homologous series of dicarboxilic acid derivatized resolving agents of racemic 1-phenylethylamine. Resolution results obtained with the oxalic, malonic, and succinic acid derivatives were previously discussed(1). Each of the above derivative resolving agents could be successfully applied as resolving agents of 1-phenylethylamine. The efficiency of the present optical resolution using (+)-(R)-N-(1-phenylethyl)glutaramic acid resolving agent was remarkably inferior to the results obtained by its shorter chained homologues(1). Use of achiral additives, like urea, thiourea, N-methylurea, and N,N'-dimethylurea caused large increase in the efficiency of the resolution by (+)-(R)-N-(1-phenylethyl)glutaramic acid resolving agent. Precipitated salts obtained in the resolutions performed in the presence of the additives were investigated by thermoanalysis, X-ray powder diffraction, and optical microscopy. Based on the analytical data, the improvement of the resolution results was attributed to the influence of the additives on the crystal nucleation processes of the diasteromeric salts.     

Acute, sublethal and combination effects of azadirachtin and Bacillus thuringiensis toxins on Helicoverpa armigera (Lepidoptera: Noctuidae) larvae

The efficacy of neem (1500 ppm azadirachtin (AI)), Delfin WG, a biological insecticide based on selected strain of Bacillus thuringiensis Berliner (Bt) subspecies kurstaki, and Cry1Ac protein, either individually or in combination, were examined against first to fourth instar Helicoverpa armigera (Hübner) larvae. Using an oral administration method, various growth inhibitory concentrations (EC) and lethal concentrations (LC) were determined for each bioagent. Combinations of sublethal concentrations of Bt spray formulation with azadirachtin at EC50 or EC95 levels not only enhanced the toxicity, but also reduced the duration of action when used in a mixture. The LC20 and LC50 values for Cry1Ac toxin were 0.06 and 0.22 microg ml-1, respectively. Bt-azadirachtin combinations of LC50+EC20 and LC50+EC50 result in 100% mortality. The mortality also was significant in LC20+EC20 and LC20+EC50 mixtures. These studies imply that the combined action is not synergistic but complimentary, with azadirachtin particularly facilitating the action of Bt. The Bt spray-azadirachtin combination is more economical than combinations that involve isolating the toxic protein, as the Bt spray formulations can be combined in a spray mixture with neem. These combinations may be useful for controlling bollworm populations that have acquired resistance to Bt as they may not survive the effect of mixture. Azadirachtin may be useful as a means of reducing the endotoxin concentrations in a mixture, to promote increased economic savings and further reduce the probability of resistance development to either insect control agent.     

降解剂对森林凋落物可溶性有机碳含量的影响及凋落物降解模式比较研究

森林凋落物是森林生态系统中可溶性有机碳(DOC)的主要来源,在生态系统碳循环过程中起重要作用。以帽儿山地区胡桃楸、兴安落叶松以及胡桃楸-兴安落叶松人工林凋落物为研究对象,通过液体发酵培养将纤维素高效降解真菌Peniophora intranata与Sarocladium strictum制成单一(A菌剂、B菌剂)及混合菌剂(C菌剂),测定野外条件下经降解剂处理的凋落物基质在不同时期的DOC含量,分析降解剂对不同类型森林凋落物DOC动态变化的影响,并比较各凋落物基质降解模式异同。结果表明：(1)凋落物基质DOC含量在降解剂处理后均随降解时间增加呈下降趋势,且下降幅度大小表现为混合基质>胡桃楸基质>落叶松基质;在最初的1个月,各凋落物基质DOC含量均显著高于其他降解时期DOC含量。(2)经混合菌剂处理后的胡桃楸基质DOC含量相较于2种单一菌剂处理后的胡桃楸基质DOC含量低,而经混合菌剂处理后的兴安落叶松基质与胡桃楸-兴安落叶松基质的DOC含量未表现出相同的显著性。(3)经3种菌剂处理后的胡桃楸基质降解模式均相同,经B菌剂与C菌剂处理的落叶松基质降解模式相同,经A菌剂与C菌剂处理...     

Noninvasive monitoring of therapy-induced microvascular changes in a pancreatic cancer model using dynamic contrast-enhanced magnetic resonance imaging with P846, a new low-diffusible gadolinium-based contrast agent

A predictive technique in the management of patients with cancer could improve the therapeutic index by allowing better individualization of treatment. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a noninvasive technique that can provide anatomical and physiological information on the tumor and its microenvironment. We studied the effect of chemotherapy (gemcitabine), anti-angiogenesis therapy (sunitinib) and radiotherapy on the kinetics of DCE-MRI parameters in a preclinical model of pancreatic cancer using P846, a new low-diffusible contrast agent. Mice underwent DCE-MRI before treatment (MRI1), after 1 week of treatment (MRI2), and after 1 additional week (MRI3). Combined treatment with radiotherapy and sunitinib had a synergistic effect on tumor growth. In radiotherapy/sunitinib-treated mice, a decrease in K(trans) at MRI2 predicted its superior antivascular and antitumor effect at an early time. An increased K(trans) at MRI2, as seen in gemcitabine- and gemcitabine/sunitinib-treated mice, reflects increased permeability for P846 and might predict a smaller therapeutic effect at this early time. This study shows that the kinetics of DCE-MRI parameters depends on the contrast agent used. P846 appears to be a promising low-diffusible agent to monitor therapeutic effects in this preclinical cancer model, but further studies are needed to compare its behavior with Gd-DTPA and macromolecular-weight contrast agents. Sunitinib as a radiosensitizer is promising for future clinical trials in human pancreatic cancer.     

Blockade of constitutively activated ERK signaling enhances cytotoxicity of microtubule-destabilizing agents in tumor cells

The extracellular signal-regulated kinase (ERK) signaling pathway is constitutively activated in many human tumor cell types. Given the cytoprotective role of this pathway, we examined whether its specific blockade might sensitize human tumor cells to the induction of apoptosis by various anticancer drugs. Although blockade of ERK signaling alone did not induce substantial cell death, it resulted in marked and selective enhancement of the induction of apoptosis by microtubule-destabilizing agents in tumor cells in which the ERK pathway is constitutively activated. The synergistic activation of c-Jun NH₂-terminal kinase by the combination of an ERK pathway inhibitor and a microtubule-destabilizing agent appeared to be responsible, at least in part, for this effect. These results suggest that administration of the combination of an ERK pathway inhibitor and a microtubule-destabilizing agent is a potential chemotherapeutic strategy for the treatment of tumor cells with constitutive activation of the ERK pathway.     

Synergistic effect of prostaglandin F2alpha and cyclic AMP on glucose transport in 3T3-L1 adipocytes

The combined effect of prostaglandin F2alpha (PGF2alpha) and cAMP on glucose transport in 3T3-L1 adipocytes was examined. In cells pretreated with PGF2alpha and 8-bromo cAMP for 8 h, a synergy between these two agents on glucose uptake was found. Insulin-stimulated glucose transport, on the other hand, was only slightly affected. The synergistic effect of these two agents was suppressed in the presence of cycloheximide and actinomycin D. In concord, immunoblot and Northern blot analyses revealed that GLUT1 protein and mRNA levels were both increased in cells pretreated with both PGF2alpha and 8-bromo cAMP, greater than the additive effect of each agent alone. The synergistic action of PGF2alpha with 8-bromo cAMP to enhance glucose transport was inhibited by GF109203X, a selective protein kinase C (PKC) inhibitor. In addition, in cells depleted of diacylglycerol-sensitive PKC by prolonged treatment with 4beta-phorbol 12beta-myristate 13alpha-acetate, a PKC activator, the synergistic effects of PGF2alpha and 8-bromo cAMP on glucose transport and GLUT1 mRNA accumulation were both abolished. Taken together, these results indicate that PGF2alpha may act with cAMP in a synergistic way to increase glucose transport, probably through enhanced GLUT1 expression by a PKC-dependent mechanism.     

Establishment, Survival and Activity of the Biocontrol Agents Pichia guilermondii and Bacillus mycoides Applied as a Mixture on Strawberry Plants

Establishment and survival of two biocontrol agents, the yeast Pichia guilermondii isolate Y2, and one of two isolates of the bacterium Bacillus mycoides (B16 and B17), were studied in commercial-like greenhouse experiments. The establishment of the biocontrol agents and their survival on strawberry leaflets and fruitlets were recorded in two experiments. Bacterial populations and their rate of decline over time did not differ significantly when applied alone or in a mixture with the yeast. In most cases, the results were similar for the yeast, but in two out of 27 comparisons the yeast populations, when applied in a mixture with the bacterium, were significantly larger than when applied separately. The biocontrol activity of the yeast and the bacterium against Botrytis cinerea on strawberry plants was examined in two experiments. In one experiment, the biocontrol agents reduced the number of diseased fruits by 50% when applied alone, whereas their mixture resulted in a 75% disease reduction. In this case, the effect of the biocontrol agnets in the mixture was additive. In a second experiment, the same yeast isolate and the other bacterial isolate (B17) were combined. The biocontrol agents did not significantly reduce the disease when applied separately. However, their mixture resulted in a synergistic effect and disease suppression was significantly improved compared to the biocontrol agents applied alone.