Hasil untuk "Chemistry"

C. Ingold

C. May

I. Mills

F. G. Mann, B. Saunders

E. Block

J. Peters, D. V. Slyke

V. Balzani

Chao‐Jun Li, B. Trost

P. Thevenot, Wenjing Hu, Liping Tang

Christopher D. Hein, Xin-ming Liu, Dong Wang

Click chemistry refers to a group of reactions that are fast, simple to use, easy to purify, versatile, regiospecific, and give high product yields. While there are a number of reactions that fulfill the criteria, the Huisgen 1,3-dipolar cycloaddition of azides and terminal alkynes has emerged as the frontrunner. It has found applications in a wide variety of research areas, including materials sciences, polymer chemistry, and pharmaceutical sciences. In this manuscript, important aspects of the Huisgen cycloaddition will be reviewed, along with some of its many pharmaceutical applications. Bioconjugation, nanoparticle surface modification, and pharmaceutical-related polymer chemistry will all be covered. Limitations of the reaction will also be discussed.

David M. Pereira, P. Valentão, J. Pereira et al.

In recent years, few classes of natural products have received as much attention as phenolics and polyphenols. This special issue of Molecules, “Phenolics and Polyphenolics”, is a remarkable confirmation of this trend. Several aspects related to phenolics chemistry, comprising the several classes, will be discussed. In addition, the increasing interest in phenolics’ biological activities is covered, and several works addressing this matter are referred.

M. Alcarazo, C. Lehmann, A. Anoop et al.

Yanjie Zhang, P. Cremer

P. Sun, D. Armstrong

T. Klapötke

This graduate-level textbook treats the basic chemistry of high energy materials - primary and secondary explosives, propellants, rocket fuel and pyrotechnics - and provides a review of new research developments. Applications in both military and civil fields are discussed. This book also offers new insights into 'green' chemistry requirements and strategies for military applications. This work should be of interest to advanced students in chemistry, materials science and engineering, as well as all those working in defense technology.

V. Talanquer

Lanbo Lai, Xiaolin Wang, Gholamreza Kefayati et al.

The indirect evaporative cooling system, which exploits the water evaporation process to generate cooling loads without introducing additional moisture, has been recognised as a viable alternative to conventional air-conditioning systems. This acknowledgment is due to its attributes of energy efficiency and environmental friendliness. The meticulous selection of wetting materials for an indirect evaporative cooler is of paramount importance as it significantly influences the heat and mass transfer performance of the system. Therefore, this paper experimentally examined a novel material produced by laser-resurfaced technology, and this material was compared with four other distinct materials (kraft paper, cotton fibre, polyester fibre, and polypropylene + nylon fibre) while considering the wicking ability, water-holding capacity, and thermal response performance. The results revealed that the fabric materials, specifically cotton fibre and polyester fibre, exhibited outstanding water-wicking ability, with a vertical wicking distance exceeding 16 cm. Cotton fibre also demonstrated an exceptional water-holding ability, registering a value of 0.0754 g/cm². In terms of thermal response performance, polypropylene + nylon fibre and the laser-resurfaced polymer achieved stable conditions within one minute, which could be attributed to the absence of a mechanical support plate and adhesive layer. All five materials attained stability after 4.2 min. Cotton and polyester fibres exhibited advantages in the duration of the evaporation process, maintaining stable conditions for 24 and 90 min, respectively. Based on the experimental results, appropriate water-spray strategies are proposed for each material.

Riley B. Jackson, Tyler M. Wilson, Joseph S. Wilson et al.

<i>Lavandula angustifolia</i> Mill., lavender, is an aromatic plant in the Lamiaceae family. Lavender, which is native to the Mediterranean region but cultivated throughout the world, is an important economic plant. Several studies have investigated two aspects of this aromatic plant: (1) which pollinators, particularly bees, pollinate lavender, and (2) the composition of lavender essential oil. However, little research has been conducted to investigate how pollination affects either the yield or phytochemistry of lavender. The current study, which was conducted in North America, investigates which bee species visit lavender and how pollination affects plant chemistry, specifically the essential oil produced by lavender. Over the course of the 5-week observational period, a total of 12 species (across 10 genera) of bees were identified visiting lavender. Compared to previous studies on cultivated lavender at the same site (Mt. Nebo Botanical Farm, Mona, UT), four bee species not previously observed on lavender were identified. These included <i>Hoplitis producta</i>, <i>Nomada</i> sp., <i>Osmia trevoris</i>, and <i>Megachile snowi</i>. Pollinated lavender, compared to lavender excluded from pollinators, produced more essential oil (yield (<i>w</i>/<i>w</i>) = 1.49% vs. 1.07%), lower relative amounts of linalool (35.4% vs. 39.9%), and higher relative amounts of linalyl acetate (21.3% vs. 16.8%). The findings of this study demonstrate the ecological interactions between pollinators and lavender, and how those interactions impact phytochemistry.

Janine H. Peterson, Lixinhao Yang, James C. Gumbart et al.

ABSTRACT Almost all integral membrane proteins that reside in the outer membrane (OM) of gram-negative bacteria contain a closed amphipathic β sheet (“β barrel”) that serves as a membrane anchor. The membrane integration of β barrel structures is catalyzed by a highly conserved heterooligomer called the barrel assembly machine (BAM). Although charged residues that are exposed to the lipid bilayer are infrequently found in outer membrane protein β barrels, the β barrels of OmpC/OmpF-type trimeric porins produced by Enterobacterales contain multiple conserved lipid-facing basic residues located near the extracellular side of the OM. Here, we show that these residues are required for the efficient insertion of the Escherichia coli OmpC protein into the OM in vivo. We found that the mutation of multiple basic residues to glutamine or alanine slowed insertion and reduced insertion efficiency. Furthermore, molecular dynamics simulations provided evidence that the basic residues promote the formation of hydrogen bonds and salt bridges with lipopolysaccharide, a unique glycolipid located exclusively in the outer leaflet of the OM. Taken together, our results support a model in which hydrophilic interactions between OmpC and LPS help to anchor the protein in the OM when the local environment is perturbed by BAM during membrane insertion and suggest a surprising role for membrane lipids in the insertion reaction.IMPORTANCEThe assembly (folding and membrane insertion) of bacterial outer membrane proteins (OMPs) is an essential cellular process that is a potential target for novel antibiotics. A heterooligomer called the barrel assembly machine (BAM) plays a major role in catalyzing OMP assembly. Here, we show that a group of highly conserved lipid-facing basic residues in Escherichia coli OmpC, a member of a major family of abundant OMPs known as trimeric porins, is required for the efficient integration of the protein into the outer membrane (OM). Based on our work and previous studies, we propose that the basic residues form interactions with a unique OM lipid (lipopolysaccharide) that promotes the insertion reaction. Our results provide strong evidence that interactions between specific membrane lipids and at least a subset of OMPs are required to supplement the activity of BAM and facilitate the integration of the proteins into the membrane.

Yaschilal Muche Belayneh, Getnet Mengistu, Kidan Hailay

Background: Liver disease is any disease that negatively affects the normal function of the liver, and it is a major health problem that challenges not only healthcare professionals, but also the pharmaceutical industry and drug regulatory agencies. Similarly, diarrhea is the second leading cause of death among children under five globally next to pneumonia. The available synthetic drugs for the treatment of liver disorders and diarrhoea have limited safety and efficacy. Objective: To evaluate the in vivo hepatoprotective and antidiarrheal activities of hydroalcoholic leaf and fruit extracts of Schinus molle L. (Anacardiaceae) in mice. Methods: Hepatoprotective activity of the extracts was evaluated by using CCl4 induced hepatotoxicity in mice model. In this model, mice were divided into groups and treated as follows. The normal control and toxicant control groups were treated with the vehicle used for reconstitution, the positive control was treated with the standard drug (silymarin), and the test groups were treated with different doses of plant extracts daily in the morning for seven days. Additionally, all groups except the normal control were treated with CCl4 (2 mg/kg, IP) on the 4th day of treatment, 30 min post-dose. On the 7th day, blood was collected from each mouse via a cardiac puncture. The collected blood was centrifuged, and serum levels of ALT, AST, and ALP were determined using an automated chemistry analyser. Data were analysed using one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test.The antidiarrheal activity of the extract was investigated using castor oil-induced diarrhoea, enteropooling, and small intestine transit. The test groups received various doses (100, 200, and 400 mg/kg) of the extract, whereas the positive control received loperamide (3 mg/kg), and the negative control received the vehicle (distilled water, 10 ml/kg). Result: Hepatoprotective activity: The leaf and fruit crude extracts showed significant improvement in the body weight and liver weight of mice compared to the untreated toxicant control. Additionally, treatment with hydromethanol leaf and fruit extracts caused a significant (P < 0.05) improvement in liver biomarkers compared to the toxicant control. Similarly, the n-butanol and chloroform fractions of the fruit extract caused a significant reduction (P < 0.01) in serum AST, ALT, ALP and Bilirubin levels and a significant (P < 0.001) increase in total protein compared to the toxicant control. However, none of the three solvent fractions (n-butanol, chloroform, and aqueous) of the fruit extract significantly affected (P > 0.05) the level of albumin compared with the toxicant control.Antidiarrheal activity: In the castor oil-induced diarrheal model, the 80 % methanol extract delayed the onset of defaecation and significantly reduced the number and weight of faeces at all tested doses compared to the negative control. In the enteropooling test, 80 ME significantly (P < 0.001) reduced the weight and volume of intestinal fluid at all tested doses compared with the negative control. Results from the charcoal meal test revealed that the extracts produced a significant anti-motility effect at all tested doses compared with the negative control. Conclusion: This study confirmed the hepatoprotective and antidiarrheal activities of hydroalcoholic extracts. The highest test dose produced the maximum hepatoprotective and antidiarrheal activities in all models.