Thin Organic Membrane Research Articles

The argonaut constructs its shell via physical self-organization and coordinated cell sensorial activity

SummaryThe shell of the cephalopod Argonauta consists of two layers of fibers that elongate perpendicular to the shell surfaces. Fibers have a high-Mg calcitic core sheathed by thin organic membranes (>100 nm) and configurate a polygonal network in cross section. Their evolution has been studied by serial sectioning with electron microscopy-associated techniques. During growth, fibers with small cross-sectional areas shrink, whereas those with large sections widen. It is proposed that fibers evolve as an emulsion between the fluid precursors of both the mineral and organic phases. When polygons reach big cross-sectional areas, they become subdivided by new membranes. To explain both the continuation of the pattern and the subdivision process, the living cells from the mineralizing tissue must perform contact recognition of the previously formed pattern and subsequent secretion at sub-micron scale. Accordingly, the fabrication of the argonaut shell proceeds by physical self-organization together with direct cellular activity.

Characterization of the Multicellular Membrane‐Bearing Algae From the Kuanchuanpu Biota (Cambrian: Terreneuvian)

AbstractThe diversity of small shelly fossils (SSFs) demonstrates that multicellular organisms underwent large‐scale radiation at the beginning of the Cambrian, which is highlighted by the coexistence of various metazoans and the occurrence of their embryo fossils. However, little is known about early Cambrian eukaryotic multicellular algae, the primary producers that replaced oxygenic cyanobacteria and played a crucial ecological role in matter cycling and energy dynamics in marine ecosystems. In this study, hundreds of microscopic three‐dimensionally preserved multicellular aggregate fossils were obtained from the Kuanchuanpu Formation (Cambrian: Terreneuvian, ca. 535 Ma) in southern Shaanxi, South China, which consisted of several tightly packed multicellular clumps encapsulated in a thin organic membrane. Synchrotron tomography analysis further revealed that the cells of the whole aggregate, although partitioned into different clumps by a gelatinous membrane, were distinctly differentiated into an outer conical cell layer and an inner spherical‐cell layer, thus suggesting of a cortex‐medulla‐like differentiation. These characteristics resemble those of multicellular algae (e.g.,Wengania,Gremiphyca, andThallophyca) from the Weng'an biota (Ediacaran, South China) in morphology, size, and internal cell structure. Furthermore, a potential asexual life cycle for these membranous algae was proposed based on their morphological and structural characteristics.

Sabellaria alveolata sandcastle worm from the Mediterranean Sea: new insights on tube architecture and biocement.

The Atlantic-Mediterranean polychaete Sabellaria alveolata lives in agglutinated tubes adjoined to each other to form discrete reef-like bioconstructions in shallow-water settings characterised by high hydrodynamic energy where sediment particles are constantly resuspended. Tubes are built with sand grains glued by proteinaceous secretions. Analyses of a reef fragment collected near Sampieri (SE Sicily, Sicily Strait) allowed the first detailed description of the tube architecture and biocement of this worms from the Mediterranean. The tube consists of an inner thin organic membrane and three agglutinated layers including: (a) a thin inner layer of flat grains arranged side by side; (b) a thick mid layer with a frame of relatively large sub-rounded grains with cavities partly filled by small grains; and (c) a thin outer layer of large, flat to curved, usually biogenic clasts diverging towards the opening. This particular architecture is distinctive of the family. Morphological and epifluorescence observations revealed that biocement consists of drops at the contact between sub-spherical grains and strips along edges of flat grains. Biocement is a solid foam-like material characterised by high abundance of carbon; the presence of phosphorous and nitrogen confirms its proteinaceous composition. Due to the electrostatic interaction with the proteins, calcium and magnesium are most likely complexed to the cement rather than being trapped in the cells. These elements contribute to the solidification of the glue and stabilisation of the tube structure. However, the organic nature of cement and the high energy of their habitat, make sabellariid reefs dynamic and ephemeral, and the preservation as fossils unlikely, with a confident record only extending back to the Miocene.

Voltammetry Study of an Anti-HIV Compound by means of a Thin Organic Membrane

Cyclic and square wave voltammetries have been used to study electrochemical behaviour of an anti-HIV agent (Guttiferone A) at the liquid-liquid interface. The thin organic membrane is formed by an organic solvent containing redox probe. Guttiferone A, a benzophenone (BP) with appropriate electrolyte. It is demonstrated that BP possesses three reduction systems due to the redox transformation of the three tautomeric forms that lead to the migration of proton between the hydroxyl group in position 4 and the carbonyl group in positions 2 and 10. The transfer of proton from the aqueous solution to the organic phase is crucial for the redox transformation of BP into the organic membrane. The voltammograms obtained are strongly influenced by the pH of the aqueous phase. The electrochemical mechanism consists of 2e−/2H+exchange to form the separate redox compound BPH2.

Electromembrane Extraction: A New Technique for Accelerating Bioanalytical Sample Preparation

The recent societal requirements to explore more environmentaly friendly solutions in the field of sample preparation have gained increasing focus during recent years. A reduction in the consumption of hazardous organic solvent owing to environmental and cost perspectives, small amounts of sample available and time reduction, have been major incentives for scientists to miniaturize existing sample preparation methods. Some of these challenges were addressed by the introduction of electromembrane extraction (EME), a totally new extraction principle where a potential difference is applied across a thin organic membrane immobilized in the pores in the wall of a porous polypropylene membrane. The potential difference is utilized to extract charged analytes of interest from the sample, across the organic membrane, and into an aqueous acceptor solution present inside the lumen of the hollow fiber. This article focuses on the potential of EME in bioanalysis, including discussions of EME performance.

Electrochemistry of coupled electron-ion transfer of a heme-like complex in an artificial organic membrane

The electrochemistry of a heme-like complex 5,10,15,20-tetraphenylporphyriniron(III) chloride (Fe(III)–TPP–Cl) embedded in a lipophilic artificial membrane is studied by means of voltammetric techniques. The experimental system used comprises of a thin organic membrane hosting the redox probe, sandwiched between edge plane pyrolytic graphite electrode and an aqueous electrolyte solution. In the course of the voltammetric experiment the redox transformation of Fe(III)–TPP–Cl at the electrode|membrane interface is accompanied by concomitant ion transfer reactions across the membrane|water interface. The overall electrochemical process proceeds as a coupled electron–ion transfer reaction providing insight into energetic and kinetic aspects of the complex membrane charge-transfer reactions. The membrane electrochemistry of Fe(III)–TPP–Cl involves two quasireversible redox transformations typical for the Fe(III)/Fe(II) couple. Both redox processes are coupled with a chemical reactions proceeding inside the membrane as well as by complex ion transfer reactions across the membrane|water interface comprising chloride expulsion from the membrane and cation ingress from the aqueous phase.

Formation of magnetite by bacteria and its application.

Magnetic particles offer high technological potential since they can be conveniently collected with an external magnetic field. Magnetotactic bacteria synthesize bacterial magnetic particles (BacMPs) with well-controlled size and morphology. BacMPs are individually covered with thin organic membrane, which confers high and even dispersion in aqueous solutions compared with artificial magnetites, making them ideal biotechnological materials. Recent molecular studies including genome sequence, mutagenesis, gene expression and proteome analyses indicated a number of genes and proteins which play important roles for BacMP biomineralization. Some of the genes and proteins identified from these studies have allowed us to express functional proteins efficiently onto BacMPs, through genetic engineering, permitting the preservation of the protein activity, leading to a simple preparation of functional protein-magnetic particle complexes. They were applicable to high-sensitivity immunoassay, drug screening and cell separation. Furthermore, fully automated single nucleotide polymorphism discrimination and DNA recovery systems have been developed to use these functionalized BacMPs. The nano-sized fine magnetic particles offer vast potential in new nano-techniques.

Origin of the lower jaw in cephalopods: a biting issue

A survey of serial, histological sections of cephalopod embryos at early and advanced morphogenetic stages provided evidence that always the cutting edge of the lower jaw is first connected, by a thin organic membrane, to the cutting edge of the upper jaw. The lower jaw rudiment does not exhibit any separation of the right from the left half. The evolutionary origin of the lower jaw, which has no obvious homologue in other molluscs, remains a matter of debate.

Micro-bubble formation with organic membrane in a multiphase microfluidic system

This paper describes the continuous and uniform organic encapsulated micro-bubble generation system in a water flow microchannel including a lumped gas and organic injection junction. The micro-bubble was formed by the blow of organic phase into a water phase in microchannel and the gas was encapsulated in the thin organic membrane. Multiphase microchemical systems provide the large interfacial area, fast mixing and fast reaction efficiency to achieve increased performance in microfluidic system. The diameter and thickness of organic micro-bubble were well controlled by the flow rates of water phase and organic phase. The diameter of the gas bubble encapsulated organic membrane was ranged from 110 μm to 220 μm, while the thickness of organic membrane from 4 μm to 16 μm. The generation rate of organic micro-bubble was 40 numbers per second with the uniform volume controllable, ranging from 214 pL to 855 pL. The organic membrane is applicative for the chemical reaction media, and the organic bubble is expected to apply as capsules of reactive gas handling in microfluidic system.

Molecular Mechanism of Magnet Formation in Bacteria.

Magnetic bacteria have an ability to synthesize intracellular ferromagnetic crystalline particles consisting of magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ) which occur within a specific size range (50–100 nm). Bacterial magnetic particles (BMPs) can be distinguished by the regular morphology and the presence of an thin organic membrane enveloping crystals from abiologically formed magnetite. The particle is the smallest magnetic crystal that has a regular morphology within the single domain size. Therefore, BMPs have an unfathomable amount of potential value for various technological applications not only scientific interests. However, the molecular and genetic mechanism of magnetite biomineralization is hardly understood although iron oxide formation occurs widely in many higher animals as well as microorganisms. In order to elucidate the molecular and genetic mechanisms of magnetite biomineralization, a magnetic bacterium Magnetospirillum sp. AMB-1, for which gene transfer and transposon mutagenesis techniques had been recently developed, has been used as a model organism. Several findings and information on the BMPs formation process have been obtained within this decade by means of studies with this model organism and its related one. Biomineralization mechanism and potential availability in biotechnology of bacterial magnets have been elucidated through molecular and genetic approach.

Scanning electron microscope observations on the tube of the reef‐forming serpulidFicopomatus enigmaticus(Fauvel) (Annelida, Polychaeta)

Abstract The tube of Ficopomatus enigmaticus (Fauvel) has two different layers: an outer, 90 μm‐thick calcareous one and an inner, very thin organic membrane. Prismatic crystals, about 5 μm in length, are evident at the inner surface of the calcareous layer. In the reef‐like aggregates, tubes grow perpendicular to the substratum and are closely packed: their density ranges from 70 000 to 180 000 worms‐m‐2, and distance between tube mouths averages 1.2 mm. Adherence between tubes appears to be due to wedge‐shaped junctions, consisting of 10–12 μm‐long clusters of crystals. Small tubes of newly settled individuals encrust interweaving adult tubes and help to consolidate the reef framework.

Biology and ultrastructure of the mycophagus, soil testate amoeba, Phryganella acropodia (Rhizopoda, Protozoa)

Clones of Phryganella acropodia were cultivated under different trophic conditions with bacteria as the food source. The doubling time was estimated to be 3 days. The edibility of four species of fungi, Aspergillus niger, Cunninghamella echinulata, Penicillium echinulatum and Stilbella bulbicola, was tested, but only Penicillium enchinulatum and Stilbella bulbicola were eaten and digested by the amoeba. An ultrastructure examination showed that there are two contractile vacuoles, many dictyosomes, a single nucleus with several nucleoli, and peroxisomes. The pseudopodia are filiform when attached to the substrate but change to lobose when the animal is floating. A thin organic membrane covers the aperture of resting forms.

Organic thin membranes and their function for separation.

The efforts for preparing functional organic thin membranes are now being continued extensively. A novel stage of the organic thin layers with good separation properties was initiated by the successful preparation of asymmetric membranes for reverse osmosis by Loeb and Sourirajan. In these membranes the thin layers with active properties for separation are formed with the supporting layers by the phase-separation mechanism. In continual efforts to develop novel and high speciality functions, very thin organic membranes, such as monolayers and bilayers, have been prepared and made functional. These processes and future problems are briefly reviwed.