THE THEORY OF LIQUID-CRYSTAL BIOMEMBRANES

In 1992 the Overseas Chinese Physicists, Association (OCPA) established an Outstanding Young Researcher Award to promote research in physics.The Award is to recognize outstanding work done by young overseas Chinese physicists in Europe and America.The candidates are nominees from research institutions in both continents.In 1993 OCPA set up another award,the OCPA Achievement in Asia Award. to encourage research achievements that are being done by

Combined effects of headgroup charge and tail unsaturation of lipids on lateral organization and diffusion of lipids in model biomembranes

Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive.In this paper,using coarse-grained molecular dynamics simulation,we theoretically study the combined effects of headgroup charge and tail unsaturation of lipids on the lateral organization and diffusion of lipids in ternary lipid bilayers.In neutral ternary lipid bilayers composed of saturated lipids,unsaturated lipids,and cholesterols,under the conditions of given temperature and components,the main factor for the phase separation is the unsaturation of unsaturated lipids and the bilayers can be separated into liquid-ordered domains enriched in saturated lipids and cholesterols and liquid-disordered domains enriched in unsaturated lipids.Once the headgroup charge is introduced,the electrostatic repulsion between the negatively charged lipid headgroups will increase the distance between the charged lipids.We find that the lateral organization and diffusion of the lipids in the（partially） charged ternary lipid bilayers are determined by the competition between the headgroup charge and the unsaturation of the unsaturated lipids.In the bilayers containing unsaturated lipids with lower unsaturation,the headgroup charge plays a crucial role in the lateral organization and diffusion of lipids.The headgroup charge may make the lipid domains unstable and even can suppress phase separation of the lipids in some systems.However,in the bilayers containing highly unsaturated lipids,the lateral organization and diffusion of lipids are mainly dominated by the unsaturation of the unsaturated lipids.This work may provide some theoretical insights into understanding the formation of nanosized domains and lateral diffusion of lipids in plasma membranes.

Integral Theorems Based on a New Gradient Operator Derived from Biomembranes (Part I): Fundamentals

A new gradient operator was derived in recent studies of topological structures and shape transi- tions in biomembranes. Because this operator has widespread potential uses in mechanics, physics, and biology, the operator’s general mathematical characteristics should be investigated. This paper explores the integral characteristics of the operator. The second divergence and the differential properties of the operator are used to demonstrate new integral transformations for vector and scalar fields on curved surfaces, such as the second divergence theorem, the second gradient theorem, the second curl theorem, and the second circulation theorem. These new theorems provide a mathematical basis for the use of this operator in many disciplines.

Integral Theorems Based on a New Gradient Operator Derived from Biomembranes (Part II): Applications

Based on the second gradient operator and corresponding integral theorems such as the second divergence theorem, the second gradient theorem, the second curl theorem, and the second circulation theorem on curved surfaces, a few new scalar differential operators are defined and a series of integral transformations are derived. Interesting transformations between the average curvature and the Gauss cur- vature are presented. Various conserved integrals related to the Gauss curvature and the second fundamental tensor are disclosed. The important applications of the results in disciplines such as the geometry, physics, mechanics, and biology are briefly discussed.

MOLECULAR UNDERSTANDING OF NATURAL POLYPHENOLS: FREE RADICAL SCAVENGING AND INTERACTION WITH BIOMEMBRANES

Quantum calculations(mainly DFT)and molecular dynamics are increasingly effective tools to evaluate the physical chemical properties of natural and bio-inspired compounds.Free Radical Scavenging Capacity.Thermodynamic parameters(mainly bond dissociation enthalpies(BDE)of the O-H phenolic bond)allowed an accurate prediction of the antioxidant capacities of

Computation of Two-Phase Biomembranes with Phase Dependent Material Parameters Using Surface Finite Elements

The shapes of vesicles formed by lipid bilayers with phase separation are governed by a bending energy with phase dependent material parameters together with a line energy associatedwith the phase interfaces.We present a numericalmethod to approximate solutions to the Euler-Lagrange equations featuring triangulated surfaces,isoparametric quadratic surface finite elements and the phase field approach for the phase separation.Furthermore,the method involves an iterative solution scheme that is based on a relaxation dynamics coupling a geometric evolution equation for the membrane surface with a surface Allen-Cahn equation.Remeshing and grid adaptivity are discussed,and in various simulations the influence of several physical parameters is investigated.

The growth of biopolymers and natural earthen sources as membrane/separator materials for microbial fuel cells:A comprehensive review

Microbial fuel cell(MFC)technology has emerged as an effective solution for energy insecurity and bioremediation.However,identifying suitable components(particularly separators or membranes)with the required properties,such as low cost and high performance,remains challenging and restricts practical application.Commercial membranes,such as Nafion,exhibit excellent performance in MFC.However,these membranes have high production costs,which considerably increase the overall MFC unit cell cost.Among the numerous types,the separators or membranes developed from biopolymers and naturally occurring earthen sources have proven to be a novel and efficient concept due to their natural abundance,cost-effectiveness(approximately$20 m^(-2),$5 m^(-2),and$1 kg-1for biopolymers,ceramics,and earthensources,respectively),structural properties,proton transportation,manufacturing and modification ease,and environmental friendliness.In this review,we emphasize cost-effective renewable green materials(biopolymers,bio-derived materials,and naturally occurring soil,clay,ceramics or minerals)for MFC applications for the first time.Biopolymers with good thermal,mechanical,and water retention properties,sustainability,and environmental friendliness,such as cellulose and chitosan,are typically preferred.Furthermore,the modification or introduction of various functional groups in biopolymers to enhance their functional properties and scale MFC power density is explored.Subsequently,separator/membrane development using various bio-sources(such as coconut shells,banana peels,chicken feathers,and tea waste ash)is described.Additionally,naturally occurring sources such as clay,montmorillonite,and soils(including red,black,rice-husk,and Kalporgan soil)for MFC were reviewed.In conclusion,the existing gap in MFC technology was filled by providing recommendations for future aspects based on the barriers in cost,environment,and characteristics.

Explore the Mystery of the Origin of the Double Helix and the Biomembrane

In nature, the most possible reason that helix is chosen as the basic structure of life molecule is based on its simplest chiral three-dimensional structure. The process of the conversion from chemical molecules to double helical molecules is completed by the topology effect which belongs to the simplest way to form helix, and no external power is needed;moreover, the energy of double helix has fixed drive direction [1]. The dual-branch loop helix (II)—the transition state of double helix has many uses, for example, it can be turned to double helix, and it may be broken into two fragments of a and b which can construct more complicated structures. So the dual- branch loop helix (II) can provide special "building block" of assembling biomembrane and other life molecules.

Mechanics of Twisted DNA Molecule Adsorbed on a Biological Membrane

DNA is the carrier of all cellular genetic information and increasingly used in nanotechnology. The study of DNA molecule achieved in vitro while submitting the DNA to all chemicals agent capabilities to destabilize links hydrogen, such as pH, temperature. In fact, the DNA enveloped in the membrane cellular, so it is legitimate to study the influence of membrane undulations. In this work, we try to show that the fluctuations of the membrane can be considerate as a physics agent is also capable to destabilize links hydrogen. In this investigation, we assume that each pair base formed an angle an with the membrane’s surface. We have proposed a theoretical model, and we have established a relationship between the angle formed by the pair base θeq and an angle formed by the membrane and each pair base. We assume that DNA and biomembrane interact via a realistic potential of Morse type. To this end, use is made of a generalized model that extends that introduced by M. Peyrard and A. R. Bishop in the past modified by M. Zoli. This generalized model is based on the resolution of a Schrödinger-like equation. The exact resolution gives the expression of the ground state, and the associated eigenvalue (energy) that equals the free energy, in the thermodynamic limit. First, we compute the denaturation temperature of DNA strands critical temperature. Second, we deduce all critical properties that mainly depend on the parameters of the model, and we quantify the effects of the membrane undulations. These undulations renormalize all physical quantities, such as harmonic stacking, melting temperature, eigenfunctions, eigenvalues and regular part of specific heat.

Molecular dynamics simulation studies of transmembrane transport of chemical components in Chinese herbs and the function of platycodin D in a biological membrane

Objective:To study the transmembrane transport of chemical components of Chinese herbs and to explore the function of platycodin D (PD) on biomembranes.Methods:Interaction between PD and the dipalmitoylphosphatidylcholine (DPPC) bilayer was reproduced by molecular dynamics simulation with the Martini force field.A model validation and methodological study were first performed,and were based on simulation investigations of transmembrane transport for three herbal compounds with distinct hydrophilic properties.Results:PD increased the mobility of the DPPC bilayer since its aglycone strongly interacted with the hydrophobic layer,which broke the structure of the gate layer,and weakened the ordered performance of hydrophobic tails.Conclusion:The Martini force field was successfully applied to the study of the interaction between herbal compounds and a biological membrane.By combining the dynamics equilibrium morphology,the distribution of drugs inside and outside the biomembrane,and the interaction sites of drugs on the DPPC bilayer,factors influencing transmembrane transport of drugs were elucidated and the function of platycodin D in a biological membrane was reproduced.

THEORY OF LC BIOMEMBRANE——A PROBE INTO SOFT CONDENSED MATTER PHYSICS

Soft condensed-state physics is a disciplinary frontier of 20th-century physics. An interdiscipline in nature, it involves biology, chemistry and even pure mathematics. Taking the liquid crystal (LC) biomembrane as an example, this article expounds the current development trend of this new and promising branch of contemporary physics.

Interactions between amphiphilic nanoparticles coated with striped hydrophilic/hydrophobic ligands and a lipid bilayer

Due to their unique physicochemical properties,nanoparticles play an important role in the fields of nanomedicine and so on.In this paper,the interactions between the nanoparticles coated with striped hydrophilic and hydrophobic ligands and a lipid bilayer are investigated by using the coarse-grained molecular dynamics simulation.This study focuses on the effects of the density of the ligands,the ratio of the hydrophilic ligands to the hydrophobic ligands,and the rigidity of the ligands on the interactions of the nanoparticles with the lipid bilayer.The results show that the nanoparticles interact with the lipid bilayer in two different ways.The nanoparticle with a small size,a large ratio of hydrophilic ligands to the hydrophobic ligands,and flexible ligands can readily be inserted into the lipid bilayer,and the nanoparticle rotation is very crucial to the insertion of the nanoparticle into the bilayer.However,the nanoparticle with a large size,a small ratio of hydrophilic ligands to hydrophobic ligands,and rigid ligands can only be adsorbed on the surface of the lipid bilayer.This work provides an effective method to modulate the interactions of the amphiphilic nanoparticles with the lipid bilayers and some insights into the applications of the nanoparticles in drug delivery,cell imaging,etc.

A mechanism study on the tamoxifen-mediated cellular internalization of liposomes

It was reported previously that tamoxifen （TAM） could increase the intracellular accumulation of drug-loaded liposomes, but the exact mechanism is unknown although it was supposed that TAM might enhance the cell uptake by inhibiting the drug efflux caused by P-glycoprotein （P-gp）. To identify the mechanism of increased cellular uptake of liposomes induced by tamoxifen, PEGgylated liposomes （SSL） ofP-gp-substrate doxorubicin （DOX） or non-P-gp-substrate coumarin （Cou） were prepared with or without TAM. The cell uptake of these liposome systems was investigated in cell lines with different P-gp-expressing levels and the interaction of TAM with lipid membrane was also studied. As the results, the co-encapsulation of TAM with DOX-SSL increased the intracellular uptake in all three tumor cell lines. In P-gp-highly-expressing MCF-7/Adr cells, the effect of TAM was the strongest and in negative control Hela cells, the impact weakened but still significant. The improvement was also observed in the cellular uptake of Cou-SSL. Surface plasmon resonance （SPR） studies demonstrated that TAM-SSL exhibited a much stronger atYmity with model biomembrane compared with empty SSL, and ft^her test with isothermal titration calorimetry （ITC） showed that free TAM had an obvious interaction with lipid membrane. In conclusion, TAM could increase the affinity of liposomes with biomembrane and enhance the intracellular accumulation of liposomes via both TAM-mediated P-gp inhibition and the increased interaction between hydrophobic TAM molecules and lipid membrane.

Conformation of liquid crystalline state in interaction between chemical materials and biomembrane in terms of modern physics

A study by the technique of modern physics has been made on the conformation of the liquid crystalline state in the interaction between chemical materials and biomembrane. The experiments have proved that the biomembrane in the liquid crystalline state can be changed from the double layer phase into the non\|double layer phase due to the influence of the outside environment. Besides the common cubic and hexagonal phases, some more other complex middle phases are also included in these non\|double layer structures, namely the lamellar\|cubic structures, the lamellar\|hexagonal structures and the cubic\|hexagonal structures. It is found that chemical materials can make the biomembrane in the liquid crystalline state assume non\|double layer structures. Their ionic radius, the van der Waals force and electrostatic interaction between the amphiphilic molecules, the electric dipole moment and pH value all have some effects on the liquid crystalline structure of biomembrane.

Interaction between curcumin and mimetic biomembrane

Curcumin, a major bioactive compound in turmeric, has a broad spectrum of antioxidant, anticarcinogenic, antimutagenic and anti-inflammatory properties. At the molecular level, curcumin modulates many structurally unrelated membrane proteins through several signaling pathways. Curcumin has been suggested to change the properties of cell membranes and affect the membrane-bound proteins indirectly; however, the detailed mechanism has yet to be investigated. In this paper, self-assembled bilayer lipid membranes are artificially constructed on the surface of a gold electrode to miinic biomembranes, and interaction between the supported membranes and curcumin is studied electrochemically. Results show that curcumin interacts with the membranes strongly, in a concentration-dependent manner. At low concentrations, curcumin tends to insert into the outer monolayer only, while at high concentrations, it may also begin to penetrate the inner monolayer. The results obtained in this work may enhance our understanding of the effect of curcumin, and possibly flavonoids, on ceU membranes and membrane proteins.

BIOMIMETIC SURFACE PREPARATION OF INERT POLYMER FILMS VIA GRAFTING LONG MONOALKYL CHAIN PHOSPHATIDYLCHOLINE

To explore construction of novel mimicking biomembrane on biomaterials surfaces, a new polymerizable phosphatidylcholine containing a long monoalkyl chain ended with acryl group （AASOPC） was designed and synthesized, which was easily derived from the terminal amino group of 9-（2-amino-ethylcarbamoyl）-nonyl-l-phosphatidyl-choline （ASOPC） reacting with acryloyl chloride. The obtained AASOPC was grafted on poly（ethylene terephthalate） （PET） via surface-initiated atom-transfer radical polymerization （SI-ATRP） to form mimicking biomembrane. These modified surface structures of PET were investigated using water contact angle （WAC）, X-ray photoelectron spectroscopy （XPS） and atomic force microscopy （AFM）. The results indicated that the new mimicking phosphatidylcholine biomembrane could be prepared on inert polymer surfaces by using the acryloyl phosphatidylcholine （AASOPC） via surface-initiated atom transfer radical polymerization （SI-ATRP）.