Liquid crystals in biology I. Historical,biological and medical aspects

In our present state of knowledge, it is useful to assume that all matter, in the solar galaxy at least, is composed of atoms and subatomic particles which function independently or interact in accordance with the laws of physics to form molecules, coacervates or other aggregates. For practical purposes, these states of matter are recognizable in the three-dimensional terrestrial world as solids, liquids and gases. This differentiation suffices also for molecular studies but, to understand the properties of mobile organic and especially of living matter fundamentally, it is necessary to investigate and conceptualize how immaterial electromagnetic and electrostatic processes produce changes in state, phase and entropy compatible with self-replication, molecular memory and vitality This possibility exists in the properties of the liquid crystal (LC) as a mesophase in thermal and optical phase transitions, i.e. as an enantiomorphic intermediate form of matter which can form complex, self-replicating, ordered structures and macromolecules, easily recognizable in everyday TV visual displays, electronic communication devices and computers. It is suggested that, in prebiotic terrestrial situations, matter possessing these properties of the LC was a precursor in the evolution of living from inanimate matter and, in the lyotropic form, in the processes of life thereafter.     

Liquid crystals in biology I. Historical, biological and medical aspects

In our present state of knowledge, it is useful to assume that all matter, in the solar galaxy at least, is composed of atoms and subatomic particles which function independently or interact in accordance with the laws of physics to form molecules, coacervates or other aggregates. For practical purposes, these states of matter are recognizable in the three-dimensional terrestrial world as solids, liquids and gases. This differentiation suffices also for molecular studies but, to understand the properties of mobile organic and especially of living matter fundamentally, it is necessary to investigate and conceptualize how immaterial electromagnetic and electrostatic processes produce changes in state, phase and entropy compatible with self-replication, molecular memory and vitality This possibility exists in the properties of the liquid crystal (LC) as a mesophase in thermal and optical phase transitions, i.e. as an enantiomorphic intermediate form of matter which can form complex, self-replicating, ordered structures and macromolecules, easily recognizable in everyday TV visual displays, electronic communication devices and computers. It is suggested that, in prebiotic terrestrial situations, matter possessing these properties of the LC was a precursor in the evolution of living from inanimate matter and, in the lyotropic form, in the processes of life thereafter.     

Acoustofluidics 10: scaling laws in acoustophoresis

In Part 10 of the thematic tutorial series "Acoustofluidics-exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation", we present and analyze a number of scaling laws relevant for microsystem acoustophoresis. Such laws are useful both in understanding, designing, and analyzing acoustofluidic devices.     

Deposition of poly(styrene/alpha-tert-butoxy-omega-vinyl-benzyl-polyglycidol) microspheres on mica plates crossing the liquid-air interface: formation of stripe pattern

Formation of stripelike assemblies of poly(styrene/alpha-tert-butoxy-omega-vinyl-benzyl-polyglycidol) microspheres adsorbed on nonpatterned mica plates moving perpendicularly from suspension of particles through the water-air interface has been observed. It was found that ordered assemblies were formed by capillary forces acting on particles crossing the water-air boundary. At sufficiently high rates of plate movement (i.e., at appropriate dynamic loading conditions) the adsorbed microspheres approaching the water surface begin sliding on the plate, due to capillary forces, in the direction opposite to the plate movement and are kept below the water surface. Plate movement brings new adsorbed particles to the water-air interface, where particles are assembled into aggregates. When particle aggregates are large, the capillary forces cannot overcome shearing forces and the particle assemblies are withdrawn on the plate above the water surface. This process repeated during continuous movement of the plate results in the formation of the quite regularly distributed stripes of adsorbed microspheres. Formation of the regularly distributed particle assemblies depends on concentration of microspheres in suspension.     

Biodynamers: self-organization-driven formation of doubly dynamic proteoids

Polypeptide-type dynamic biopolymers (biodynamers) have been generated by polycondensation via acylhydrazone and imine formation of amino-acid-derived components that polymerize driven by self-organization. They have been characterized as globular particles, reminiscent of folded proteins, by cryo-TEM, LS, DOSY NMR, and SANS studies. The reversible polymers obtained show remarkably low dispersity and feature double covalent dynamics allowing for fine-tuning of both exchange and incorporation processes through pH control. In the course of build-up, they perform a selection of the most suitable building block, as indicated by the preferential incorporation of the more hydrophobic amino-acid component with increased rate and higher molecular weight of the polymer formed. The system described displays nucleation-elongation behavior driven by hydrophobic effects and represents a model for the operation of adaptation processes in the evolution of complex matter.     

关于高分子凝聚态物理学范式的思考

每门成熟科学必然都存在一个范式,体现该门学科特殊的内在结构、基本理论框架,界定研究范围.但迄今为止,发展迅猛的高分子凝聚态物理学的范式尚未形成.本文梳理、总结了近二、三十年来高分子凝聚态物理学的重要成果,阐述并强调了软凝聚态物质、自相似、分形、标度律、关联效应、溶致凝聚、熵致相变、布朗运动、多体效应和对称破缺等基本概念及其意义,指出探究和凝练高分子凝聚态物理学的范式是摆在当前高分子物理学家面前亟待解决的问题.     

Chemically encapsulated structural elements for probing the mechanical responses of biologically inspired systems

A living cell has a crowded environment with a dense distribution of molecules that requires structured organization for its efficient functioning. One component of this structure, the actin cytoskeleton, is essential for providing mechanical support and facilitating many response activities, including the contraction of muscle cells and chemotaxis. Whereas many investigations have provided insight into the mechanical response from either an in vivo or in vitro perspective, a significant gap exists in determining how the living cell response and the polymer physics response are bridged. The understanding of these systems involves studying their components, including the individual cytoskeletal elements versus the higher-order organism organization in a living cell. Here, we leverage this organization in nature by using a chemistry-based approach to mimic the cytoskeleton in an artificial environment composed of spherically distributed lipid bilayers. This construct bears similarities to the cell membrane. To create a structurally regulated environment, we encapsulate G-actin into giant unilamellar vesicles and then polymerize actin filaments within individual liposomes. We visualize these vesicles with epifluorescence microscopy and confocal microscopy. Atomic force microscopy is then used to probe the mechanical properties of these artificial cells. This polymer cytoskeletal network appears to connect with the lipid bilayer and span the internal space within the liposomes in a manner similar to what is observed in living cells. This work will have implications in a variety of fields, including chemistry, polymer physics, structural biology, and engineering mechanics.     

Type H superconductors and the vortex lattice.

Superconducting material is used, for example, in magnetic resonance imaging for medical examinations and particle accelerators in physics. Knowledge about superfluid liquids can give us deeper insight into the ways in which matter behaves in its lowest and most ordered state. Work by the author on superconduction in liquid helium established the existence of type II superconductors and proved that vortex lattices exist in superfluid helium, in the presence of magnetic fields. He showed that the Ginzburg-Landau theory could be extended to include this "new" type of superconductors, which today are in common use. His work on phase transitions of these superconductors under the influence of magnetic fields was groundbreaking, although he has worked in many other areas since then. He was awarded the Nobel prize in 2003 "for pioneering contributions to the theory of superconductors and superfluids" with V L. Ginzburg and A. J. Leggett.     

A Perspective on the Science of Clusters

In this article, the interdisciplinary science of clusters is discussed in general terms. Different types of clusters across vast scales of matter, energy, space, and time in the physical world are discussed. Specific examples of clusters in chemistry and physics are used to illustrate various principles or models of clustering processes of atoms and molecules as well as to demonstrate the exquisite beauty and pattern of clusters and the clustering phenomena so ubiquitous in nature. Nowadays, “designer clusters” can be made with tailorable properties and used as “building blocks” to form supermolecules, or to construct large cluster-based hierarchical materials with tunable properties, or to fabricate cluster-based devices with specific functions, etc., thereby providing a materials base for nanotechnology. Clustering is a spontaneous self-assembly process and the similarity across scales reflects the intrinsic self-organization and self-similarity principle of the physical world. Geometry and symmetry transcend all clustering processes, in ordered as well as in disordered systems.     

On the study of nonlinear dynamics of complex chemical reaction systems

When driven far from equilibrium,nonlinear chemical reactions often show a variety of self-organization behavior,including chemical oscillations,waves,chaos and patterns[1].Recently,the study of such nonlinear phenomena in‘complex’systems,such as the li…     

Self-organization of molecular systems and evolution of the genetic apparatus

The aim of the work described in this report is to find pathways leading to self-organization of molecular systems. The idea is not to trace the historical pathway of evolution but to describe a model whose experimental verification should help to clarify the important principles of evolution. The difficulty of accepting the origin of living organisms as a physico-chemical phenomenon and the deeply rooted notion that a system of such complexity as the genetic apparatus could never be the outcome of processes based solely on the known laws of physics have influenced philosophical thinking very strongly. This study is also intended as an attempt to overcome this psychological problem by systematic pursuit of a model pathway composed of many, readily comprehensible steps. A process thus becomes understandable which cannot be grasped as a whole, and is therefore alien to our conceptual habits.     

Electrostatic Localization of RNA to Protocell Membranes by Cationic Hydrophobic Peptides

Cooperative interactions between RNA and vesicle membranes on the prebiotic earth may have led to the emergence of primitive cells. The membrane surface offers a potential platform for the catalysis of reactions involving RNA, but this scenario relies upon the existence of a simple mechanism by which RNA could become associated with protocell membranes. Here, we show that electrostatic interactions provided by short, basic, amphipathic peptides can be harnessed to drive RNA binding to both zwitterionic phospholipid and anionic fatty acid membranes. We show that the association of cationic molecules with phospholipid vesicles can enhance the local positive charge on a membrane and attract RNA polynucleotides. This phenomenon can be reproduced with amphipathic peptides as short as three amino acids. Finally, we show that peptides can cross bilayer membranes to localize encapsulated RNA. This mechanism of polynucleotide confinement could have been important for primitive cellular evolution.     

Ring opening metathesis polymerization catalysts

Over the past eight years, early transition metal catalysts for the ring opening metathesis polymerization of cyclic olefins have been developed. These catalysts are simple organometallic complexes containing metal carbon multiple bonds that in most cases polymerize olefins by a living process. These catalysts have been used to prepare a family of near monodispersed and structurally homogeneous polymers. A series of group VIII ROMP catalysts that allow a wide range of functionality to be incorporated into the polymer side chains have recently been prepared. This most important members of this family of complexes are the bisphosphinedihaloruthenium carbene complexes. These catalysts show excellent functional group stability and can be used to prepare well defined telechelic polymers, polyolefins with ordered functionality, and highly functionalized block copolymers.     

Self‐assembling amphiphilic block copolymer from renewable δ‐decalactone and δ‐dodecalactone

Aliphatic polyesters have many applications in the biomedical field due to their properties and facile degradation. They are commonly synthesized via ring opening polymerization (ROP) with metal‐based catalysts, but as high temperatures are needed and the products contain metal, organocatalysts are now widely adopted to polymerize them at room temperature while also ensuring short reaction times. Here, 1,7,7‐triazabicyclo[4.4.0]‐dec‐5‐ene is used to polymerize less reactive but renewably‐derived lactones, namely δ‐decalactone and δ‐dodecalactone. These monomers were chosen in the attempt of creating renewable and highly lipophilic materials for drug delivery applications as alternatives to the more traditional, but non‐renewable δ‐valerolactone and ?‐caprolactone. A combination of ROP and living radical polymerization Reversible Addition‐Fragmentation Chain Transfer is proposed here to synthesize grafted block copolymers. They are able to self‐assemble in water, forming micelles where the lipophilic polyester core is able to entrap a lipophilic drug, thus making the system a good candidate for drug delivery. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3788–3797     

Magnetic field alignment of block copolymers and polymer nanocomposites: Scalable microstructure control in functional soft materials

Block copolymers (BCPs) offer an exciting range of structures and functions that are of potential utility in existing as well as emerging technologies. Although this is generally acknowledged, with few exceptions, viable strategies for establishing scalable and robust control of BCP microstructure are underdeveloped. Magnetic field alignment offers great potential in this regard. The physics bears much in common with electric field alignment, but the absence of dielectric breakdown concerns and the more flexible, space pervasive nature of magnetic fields make it possible to design processes for high‐throughput fabrication of well‐ordered films with appropriate materials. In this perspective, we highlight the use of magnetic fields for control of microstructure in BCPs as well as polymer nanocomposites involving anisotropic nanomaterials. A brief review of efforts to date is given. Open questions related to field‐polymer interactions and future directions for magnetic alignment of these systems are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Acoustofluidics 1: Governing equations in microfluidics

In Part 1 of the thematic tutorial series "Acoustofluidics--exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation", we establish the governing equations in microfluidics. Examples of basic flow solutions are presented, and equivalent circuit modeling for determining flow rates in microfluidic networks is introduced.     

Prediction of emulsion particle sizes using a computational fluid dynamics approach

For many food products emulsification processes play an important role. Examples are ice cream, spreads, sauces, etc. As is well known, droplet break-up and coalescence phenomena are the local processes underlying the control of particle size in an emulsion process. Quite a number of studies have generated scaling laws which can be easily applied and which are useful in the design of a process. However, the prediction of particle sizes in an inhomogeneous flow, where the flow velocity is changing spatially in strength and direction and with time, is not yet well established. For one-phase flows computational fluid dynamics (CFD) methodologies are in use to predict details on the flow with quite some success. This methodology has been extended to capture the dispersed phase in an efficient way. The essence is that break-up and coalescence processes determine source terms in a transport equation for the moments of the particle size distribution, while velocity vectors as obtained in the one-phase CFD simulation determine the convective term. This method allows particle size prediction in any equipment. The approach is illustrated for the particle size evolution of an oil-in-water emulsion, for a phase-separated biopolymeric mixture (a so-called water-in-water emulsion) and for the escape of the included oil droplets from a double emulsion of the type oil-in-water-in-oil. In all cases experimental results are compared with simulation results, which match very well. This shows the strength of the method.     

Formation of Vesicles from Amphiphilic Random Copolymers in Solution: A Dissipative Particle Dynamics Simulation Study

Five coarse-grained models were built for amphiphilic random copolymers. The self-assembly of amphiphilic random copolymers in selective solvent was investigated via dissipative particle dynamics simulations. The simulation results showed that the content of hydrophilic particles and the repulsive parameter between solvent and copolymer particles were two key factors of the vesicle formation. We report herein on how to control the self-assembled morphology evolution. The two mechanisms of vesicle formation from amphiphilic random copolymers are found through investigating the dynamic processes of vesicle formation, which is in accordance with the experiment and simulation results of amphiphilic block copolymer reported in the literature.      

Researches on structural peculiarities and chemical reactions of carbazole and some of its derivatives

Dipropargyl esters of 9-ethyl, 9-n-butyl, and 9-isoamylcarbazole-3, 6-dicarboxylic acids, not hitherto described in the literature, are synthesized. It is shown that, in the presence of tert-butyl peroxide, these esters can polymerize to infusible and insoluble products.For Part XIII see [1].