Current Organic Chemistry - Volume 22, Issue 8, 2018

Background: Porous stimuli-responsive polymer membranes are a series of membrane devices with not only common separating and mechanical properties, but also stimuli-responsive capabilities. In recent decades, there is an increasing interest in utilizing track-etch polymer membranes with single or array nanochannels on them as sensing elements in smart responsive membrane devices. Objective: We review the synthesis and functionalizations of track-etch membranes and their sensing applications, in order to expand possible applications of functional organic molecules, and also supply a novel potential platform for specific analysis of organic chemistry. Method: We introduced the membrane preparation and the sensing mechanism of membrane devices, summarized recent approaches to optimize membrane functionalization. Applications: Induced by external stimuli in solutions, functional molecules fixed on track-etch membranes change their structure and ionization, which impact on the ionic permeation and ionic rectifying of these nanofluid devices. Based on this mechanism, sensing to aqueous environmental stimuli (including temperature, pH and light), specific ions and molecules have been achieved by different groups. Conclusion: For controllable pore sizes, simple modifications and regular shapes of track-etch membranes, the track-etch membranes devices exhibit specific and reliable responses to various stimuli. We hope in the future, more smart materials with specific affinities could be utilized to functionalize track-etch membrane devices, and their applications could be broadened from chemical analyses to industrial separation and purification processes.

Background: Small-angle scattering (SAS) is a powerful technique capable of determining the sample averaged structure of systems within sizes ranging from 1 nm to ~500 nm. This is particularly useful when applied to the study of self-assembled organic systems. Objective: This review article introduces the method of model-dependent analysis of small angle scattering. Method: The underlying mathematical constructs on which model-dependent analysis is based are introduced; these are developed further in practical terms through examples from recent literature. Results: Basic analysis methods are shown, in addition to more complex models for shapes and inter-particle interactions. These are demonstrated with examples from three areas of organic chemistry; small molecule surfactants, polymers, and peptides. Conclusion: The importance and applicability of small-angle scattering model-dependent analysis of complex organic molecules have been shown through both the fundamental mathematics and literature examples.

Background: Self-diffusion, the random molecular motion of molecules in the absence of a chemical potential, is readily measured with pulsed field gradient NMR techniques. Measurements of diffusion can provide information on chemical binding and porous microstructure. Objective: This manuscript describes the basics of self-diffusion measurement by NMR and provides a justification for the Stejskal-Tanner expression for free diffusive attenuation. After a discussion of the Pulsed Gradient Spin Echo (PGSE) and Pulsed Gradient STimulated Echo (PGSTE) sequences, some more specialised methods are discussed. These include: (i) A description of the effects of J-coupling during a diffusion measurement and J-compensated PGSE. J-interactions create combinations of in-phase and antiphase peaks and can make analysis difficult. (ii) Rapid NMR methods for diffusion measurement. This includes a technique enabling shorter recycle delays and circumventing the need to wait 51 for the magnetisation to recover before running the next iteration of the sequence. (iii) An introduction to obstruction and diffusion averaging effects. This is quite an involved topic but some of the fundamentals are presented here. (iv) Solvent signal suppression in high-field NMR. Solvent signals can cause problems for diffusion measurements too. The requirements for a good solvent suppression sequence are discussed followed by an introduction to the WaterControl technique. Conclusion: The variety of techniques that are presented, and which are built around PGSE/PGSTE, show the versatility of Diffusion NMR methods and provide a starting point for choosing a method or combination of methods for a wide range of applications.

In this review, we show the life cycle of parabens, commonly used preservatives that exist in nature and commercial products. Typical synthetic methods to produce parabens, and a set of complimentary characterization techniques to monitor the composition of parabens are also highlighted. This includes solid state analysis using Scanning Electron Microscope (SEM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD), in-situ monitoring of crystallization process using Focused Beam Reflectance Measurement (FBRM), Particle Vision Measurement (PVM), quantitative detection via High Performance Liquid Chromatography (HPLC), and Gas Chromatography (GC). An improved understanding of the overall physical, biophysical and chemical properties of parabens and their life cycle, summarized in this article, are vital for the safety control and extensive applications of relevant products in food, cosmetic and pharmaceutical industries.

Chemoselective ligation reactions provide facile access to various peptides and proteins including cyclic peptides, post-translationally modified proteins, and peptide/ protein probes. Recently, peptide-ligase-based chemo-enzymatic methods have emerged as promising alternatives to chemical approaches. Ligation mediated by the newly discovered butelase 1 represents one of the state-of-the-art chemo-enzymatic strategies for its high catalytic efficiency and unique substrate specificity. The butelasemediated ligation can be carried out in a semisynthetic manner, in which chemically synthesized peptides and expressed proteins are used as substrates, rendering it suitable for various applications including site-specific modification of proteins and the preparation of thioesters. In this review, we summarize the recent studies and applications of butelase 1.

Background: Biofilm is a microbial community of microbes that attach to a surface and are enclosed in an extracellular polymeric substance (EPS). Formation of these sessile communities and their inherent resistance to antimicrobial agents are the main reasons for many persistent and chronic infections. Chemotherapy of these infections is unsatisfactory for various reasons including unacceptable toxicity, poor efficacy and drug resistance. In this connection, the last few decades have witnessed wide investigations, which have been geared to investigate the anti-biofilm effects of natural products, including medicinal plant extracts and phytochemicals. Objective: This paper gives a review on the plant extracts and phytochemicals with antibiofilm capability, which hopefully provides useful information and guidance for future antimicrobial study. Method: This review is to summarize the natural products, including various phytochemicals, decoctions, plant fractions and extracts that have shown anti-biofilm activity. Literatures were collected from published articles that reported in vitro or in vivo anti-biofilm activity of natural products. Results: A total of 95 related references were found. The phytochemicals, fractions and extracts are grouped by their general classes or by their putative active components. More than 90 bioactive anti-biofilm compounds have been identified from different parts of the plants. The inhibitory concentration of the natural products was also included, and some of them were investigated for their possible anti-biofilm mechanism. Conclusion: This review has demonstrated solid evidences that plants are an excellent source to provide abundant natural compounds for the development of preventative and therapeutic agents against biofilm-based infections.

Sulfonamides are compounds with a broad spectrum of biological applications, and can act as potential medicinal molecules in drug discovery and drug development. Numerous sulfonamide-based molecules can be used to develop potent lead compounds with better efficacy and less toxicity. This review focuses on the latest information pertaining to sulfonamide derivatives having different pharmacological properties including anticancer, antiviral, antimicrobial, antibacterial, antifungal, antiinflammatory, antituberculosis, carbonic anhydrase inhibition, antimalarial, antiparasitic, anticonvulsant, and antidepressant activities, as well as carbonic anhydrase inhibitors. Relevant references have been obtained from MEDLINE (PubMed), Google Scholar, ScienceDirect, Cochrane, Scopus, SID, SciFinder, and ISI Web of Knowledge. This review article provides a literature overview of the various biological activities of sulfonamides, and covers the related literature from the last decade. It also briefly describes the therapeutic importance of sulfonamide derivatives and their pharmacological applications in a concise manner.

Sensor array methodology had attracted much attention because of its advantages in accuracy, diversity and capacities in simultaneous detection and discrimination of multiple analytes. In this study, a colorimetric sensor array comprising chloroauric acid and L-arginine mixture for the detection and identification of iron (II) ion is developed. Principal component analysis and hierarchical cluster analysis showed that the colorimetric sensor array had excellent discrimination capability to iron (II) ion. This research suggests that chloroauric acid and L-arginine mixture could act as cations chemosensor, which provides an alternative approach to design novel colorimetric sensor array.