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OPEN ACCESS PLUS
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Contents
3(2): Pp. 203 - 230
Inmaculada Aranaz, Marian Mengibar, Ruth Harris, Ines Panos, Beatriz Miralles, Niuris Acosta, Gemma Galed and Angeles Heras
[Open Access Plus] |
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Chitin and its deacetylated derivative chitosan are natural polymers composed of randomly distributed β-(1-4)- linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitin is insoluble in aqueous media while chitosan is soluble in acidic conditions due to the free protonable amino groups present in the D-glucosamine units. Due to their natural origin, both chitin and chitosan can not be defined as a unique chemical structure but as a family of polymers which present a high variability in their chemical and physical properties. This variability is related not only to the origin of the samples but also to their method of preparation. Chitin and chitosan are used in fields as different as food, biomedicine and agriculture, among others. The success of chitin and chitosan in each of these specific applications is directly related to deep research into their physicochemical properties. In recent years, several reviews covering different aspects of the applications of chitin and chitosan have been published. However, these reviews have not taken into account the key role of the physicochemical properties of chitin and chitosan in their possible applications. The aim of this review is to highlight the relationship between the physicochemical properties of the polymers and their behaviour. A functional characterization of chitin and chitosan regarding some biological properties and some specific applications (drug delivery, tissue engineering, functional food, food preservative, biocatalyst immobilization, wastewater treatment, molecular imprinting and metal nanocomposites) is presented. The molecular mechanism of the biological properties such as biocompatibility, mucoadhesion, permeation enhancing effect, anticholesterolemic, and antimicrobial has been updated.
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2(2): Pp. 153 - 158
Salla Jaakkola, Vivek Sharma and Arto Annila
[Open Access Plus] |
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Biological macromolecules, proteins and nucleic acids are composed exclusively of chirally pure monomers. The chirality consensus appears vital for life and it has even been considered as a prerequisite of life. However the primary cause for the ubiquitous handedness has remained obscure. We propose that the chirality consensus is a kinetic consequence that follows from the principle of increasing entropy, i.e. the 2nd law of thermodynamics. Entropy increases when an open system evolves by decreasing gradients in free energy with more and more efficient mechanisms of energy transduction. The rate of entropy increase is the universal fitness criterion of natural selection that favors diverse functional molecules and drives the system to the chirality consensus to attain and maintain high-entropy non-equilibrium states.
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1(2): Pp. 167 - 186
Niko Hildebrandt and Hans-Gerd Lohmannsroben
[Open Access Plus] |
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Resonance Energy Transfer (RET) plays an important role, both scientifically and commercially, in diagnostics and high throughput screening. For qualitative and quantitative analysis, RET systems are usually assembled through molecular recognition of biomolecules labeled with donor and acceptor luminophores. Lanthanide complexes, as well as quantum dot nanocrystals (QD), possess unique photophysical properties that make them especially suitable for applied RET systems in chemical biology. This review deals with the RET theory, and advantages are compared to conventional systems (using optical and other detection techniques). Different molecular recognition processes, as well as labeling techniques yielding biocompatibility are described. The photophysics of Ln complexes (e.g. millisecond luminescence decay times, line-shaped emission spectra, antenna effect of the ligand) and of QD (e.g. high extinction coefficients, size-tunable emission spectra, chemical stability) as well as their RET properties are described in detail. We give an overview of biochemical applications using lanthanide complexes and QD, e.g. immunoassays, DNA analysis and nanometer distance measurements (spectroscopic ruler) and some selected results are outlined. In particular, the recent scientific progress in biocompatible QD RET systems with the use of QD as energy donors as well as acceptors together with Ln complexes as donors is highlighted. The worldwide economic and scientific interests, as well as potentials for in vitro diagnostics (IVD) are addressed and the benefits regarding high throughput techniques, ultrahigh sensitivity, multiplexing measurements and miniaturization are discussed.
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