Journal articles: 'Active biological transport'

1

Barman, Charles R., Nevin E. Longenecker, and E. Thomas Hibbs. "Active Transport." American Biology Teacher 48, no. 5 (May 1, 1986): 304–6. http://dx.doi.org/10.2307/4448298.

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2

Fuliński, A. "Active Transport in Biological Membranes and Stochastic Resonances." Physical Review Letters 79, no. 24 (December 15, 1997): 4926–29. http://dx.doi.org/10.1103/physrevlett.79.4926.

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Fuliński, A. "Noise-stimulated active transport in biological cell membranes." Physics Letters A 193, no. 3 (October 1994): 267–73. http://dx.doi.org/10.1016/0375-9601(94)90595-9.

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Hirayama, Hirohumi, Yoshimitsu Okita, and Yuzo Fukuyama. "Optimal control of active transport across a biological membrane." Artificial Life and Robotics 2, no. 1 (March 1998): 33–40. http://dx.doi.org/10.1007/bf02471150.

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Sun, Ke, Yuejia Chen, Xialin Zhang, Changjian Zhao, and Jia Geng. "A Novel Biological Nanopore for Active DNA Transport and Detection." Biophysical Journal 114, no. 3 (February 2018): 584a. http://dx.doi.org/10.1016/j.bpj.2017.11.3194.

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Koloskova, Olesya O., Uliana A. Budanova, Inga C. Shchelik, Igor P. Shilovskii, Musa R. Khaitov, and Yurii L. Sebyakin. "Examination the Properties of Lipopeptide Liposomes Modified by Glycoconjugates." Nano Hybrids and Composites 13 (January 2017): 82–88. http://dx.doi.org/10.4028/www.scientific.net/nhc.13.82.

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Development of transport systems possessing definite physicochemical and biological properties aimed at the targeted delivery of biologically active compounds remains nowadays among urgent problems of the medicine. In this work we made physical chemical and biological tests liposomal drug delivery systems modified with glycolipids for target properties.

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Petrova, Tatiana V., and Gou Young Koh. "Biological functions of lymphatic vessels." Science 369, no. 6500 (July 9, 2020): eaax4063. http://dx.doi.org/10.1126/science.aax4063.

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The general functions of lymphatic vessels in fluid transport and immunosurveillance are well recognized. However, accumulating evidence indicates that lymphatic vessels play active and versatile roles in a tissue- and organ-specific manner during homeostasis and in multiple disease processes. This Review discusses recent advances to understand previously unidentified functions of adult mammalian lymphatic vessels, including immunosurveillance and immunomodulation upon pathogen invasion, transport of dietary fat, drainage of cerebrospinal fluid and aqueous humor, possible contributions toward neurodegenerative and neuroinflammatory diseases, and response to anticancer therapies.

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Hofmann, Alan F., Claudio D. Schteingart, and Jan Lillienau. "Biological and Medical Aspects of Active Heal Transport of Bile Acids." Annals of Medicine 23, no. 2 (January 1991): 169–75. http://dx.doi.org/10.3109/07853899109148043.

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9

Inesi, Giuseppe. "The mutual binding exclusion mechanism in active transport across biological membranes." Cell Biophysics 11, no. 1 (December 1987): 269–77. http://dx.doi.org/10.1007/bf02797124.

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Lapointe, Jean-Yves, Marilène P. Gagnon, Dominique G. Gagnon, and Pierre Bissonnette. "Controversy regarding the secondary active water transport hypothesis." Biochemistry and Cell Biology 80, no. 5 (October 1, 2002): 525–33. http://dx.doi.org/10.1139/o02-150.

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Historically, water transport across biological membranes has always been considered a passive process, i.e., the net water transport is proportional to the gradients of hydrostatic and osmotic pressure. More recently, this dogma was challenged by the suggestion that secondary active transporters such as the Na/glucose cotransporter (SGLT1) could perform secondary active water transport with a fixed stoichiometry. In the case of SGLT1, the stoichiometry would consist of one glucose molecule to two Na+ ions to 220400 water molecules. In the present minireview, we summarize and criticize the evidence supporting and opposing this water cotransport hypothesis. Published and unpublished observations from our own laboratory are also presented in support of the idea that transport-dependent osmotic gradients begin to build up immediately after cotransport commences and are fully responsible for the cell swelling observed.Key words: Xenopus oocyte, intracellular diffusion, water cotransport, SGLT1.

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Khavinson, Vladimir Khatskelevich, Natalia Sergeevna Linkova, Andrey Ivanovich Rudskoy, and Michael Gennadievich Petukhov. "Feasibility of Transport of 26 Biologically Active Ultrashort Peptides via LAT and PEPT Family Transporters." Biomolecules 13, no. 3 (March 17, 2023): 552. http://dx.doi.org/10.3390/biom13030552.

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The aim of this work is to verify the possibility of transport of 26 biologically active ultrashort peptides (USPs) into cells via LAT and PEPT family transporters. Molecular modeling and computer-assisted docking of peptide ligands revealed that the size and structure of ligand-binding sites of the amino acid transporters LAT1, LAT2, and of the peptide transporter PEPT1 are sufficient for the transport of the 26 biologically active di-, tri-, and tetra-peptides. Comparative analysis of the binding of all possible di- and tri-peptides (8400 compounds) at the binding sites of the LAT and PEPT family transporters has been carried out. The 26 biologically active USPs systematically showed higher binding scores to LAT1, LAT2, and PEPT1, as compared with di- and tri-peptides, for which no biological activity has been established. This indicates an important possible role which LAT and PEPT family transporters may play in a variety of biological activities of the 26 biologically active peptides under investigation in this study. Most of the 26 studied USPs were found to bind to the LAT1, LAT2, and PEPT1 transporters more efficiently than the known substrates or inhibitors of these transporters. Peptides ED, DS, DR, EDR, EDG, AEDR, AEDL, KEDP, and KEDG, and peptoids DS7 and KE17 with negatively charged Asp− or Glu− amino acid residues at the N-terminus and neutral or positively charged residues at the C-terminus of the peptide are found to be the most effective ligands of the transporters under investigation. It can be assumed that the antitumor effect of the KE, EW, EDG, and AEDG peptides could be associated with their ability to inhibit the LAT1, LAT2, and PEPT1 amino acid transporters. The data obtained lead to new prospects for further study of the mechanisms of transport of USP-based drugs into the cell and design of new antitumor drugs.

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Evteev, A. V., N. V. Gorbunova, O. S. Larionova, and A. V. Bannikova. "THEORETICAL SUBSTANTIATION OF DIRECT TRANSPORT OF BIOLOGICALLY ACTIVE COMPONENTS IN CONDITIONS OF MODELED GASTROINTESTINAL TRACT." Food systems 1, no. 2 (July 11, 2018): 21–28. http://dx.doi.org/10.21323/2618-9771-2018-1-2-21-28.

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In this paper, the results of studies on the release of biological active compounds from their encapsulated forms under conditions of enzymatic hydrolysis in vitro are presented. In the phase of the model «small intestine» swelling of the capsules and their subsequent decay occurs, which allows to speak about the controlled release of encapsulated bioactive components. It was revealed that almost 90 % of the residual quantity of essential ingredients was released from the capsules in the model phase of the artificial «small intestine». At the end of the experiment, the capsules released all the encapsulated biologically active substances, regardless of the content of fish oil and phenolic compounds in them. It was noted that the poly-capsules had the greatest propensity to withstand the aggressive environment of the «model stomach» and concentrate in themselves the maximum amount of biologically active substances. Mathematical modeling confirms the direct transport of biologically active compounds and the role of the swelling of capsules in the release of biologically active compounds. two mathematical models describing the classical theory of diffusion from capsules and incorporating the material relaxation coefficient demonstrate a combination of empirical and theoretical approaches in controlling the properties of encapsulated biologically active substances. the obtained data are promising in the field of development of improved and functional food products, as well as the dry ingredients and concentrates

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Dorner, Ross, John Goold, and Vlatko Vedral. "Towards quantum simulations of biological information flow." Interface Focus 2, no. 4 (March 28, 2012): 522–28. http://dx.doi.org/10.1098/rsfs.2011.0109.

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Recent advances in the spectroscopy of biomolecules have highlighted the possibility of quantum coherence playing an active role in biological energy transport. The revelation that quantum coherence can survive in the hot and wet environment of biology has generated a lively debate across both the physics and biology communities. In particular, it remains unclear to what extent non-trivial quantum effects are used in biology and what advantage, if any, they afford. We propose an analogue quantum simulator, based on currently available techniques in ultra-cold atom physics, to study a model of energy and electron transport based on the Holstein Hamiltonian. By simulating the salient aspects of a biological system in a tunable laboratory set-up, we hope to gain insight into the validity of several theoretical models of biological quantum transport in a variety of relevant parameter regimes.

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Guba, Sándor, Viola Somogyi, and Erzsébet Szabóné Bárdos. "Groundwater Remediation Using Biological And Photocatalytic Methods." Hungarian Journal of Industry and Chemistry 43, no. 1 (June 1, 2015): 39–44. http://dx.doi.org/10.1515/hjic-2015-0007.

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Abstract The degradability of two commercially available pesticides was studied using heterogeneous photocatalytic and activated sludge treatment methods. The first pesticide contained 5% quizalofop-P-ethyl as an active ingredient and petroleum naphtha as a solvent, the latter causing difficulties both in photocatalytic and biological treatment methods. The active ingredient of the second compound was acetamiprid. The photocatalysis proved to be effective both under laboratory conditions (using UV light) and when exposed to sunlight, but the pesticides remained stable during the employed biological treatment. Preliminary information on its behaviour in soil was obtained from transport modelling.

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15

Keyser, Ulrich F. "Controlling molecular transport through nanopores." Journal of The Royal Society Interface 8, no. 63 (June 29, 2011): 1369–78. http://dx.doi.org/10.1098/rsif.2011.0222.

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Nanopores are emerging as powerful tools for the detection and identification of macromolecules in aqueous solution. In this review, we discuss the recent development of active and passive controls over molecular transport through nanopores with emphasis on biosensing applications. We give an overview of the solutions developed to enhance the sensitivity and specificity of the resistive-pulse technique based on biological and solid-state nanopores.

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16

Stukel, Michael R., Moira Décima, and Michael R. Landry. "Quantifying biological carbon pump pathways with a data-constrained mechanistic model ensemble approach." Biogeosciences 19, no. 15 (August 5, 2022): 3595–624. http://dx.doi.org/10.5194/bg-19-3595-2022.

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Abstract. The ability to constrain the mechanisms that transport organic carbon into the deep ocean is complicated by the multiple physical, chemical, and ecological processes that intersect to create, transform, and transport particles in the ocean. In this paper we develop and parameterize a data-assimilative model of the multiple pathways of the biological carbon pump (NEMUROBCP). The mechanistic model is designed to represent sinking particle flux, active transport by vertically migrating zooplankton, and passive transport by subduction and vertical mixing, while also explicitly representing multiple biological and chemical properties measured directly in the field (including nutrients, phytoplankton and zooplankton taxa, carbon dioxide and oxygen, nitrogen isotopes, and 234Thorium). Using 30 different data types (including standing stock and rate measurements related to nutrients, phytoplankton, zooplankton, and non-living organic matter) from Lagrangian experiments conducted on 11 cruises from four ocean regions, we conduct an objective statistical parameterization of the model and generate 1 million different potential parameter sets that are used for ensemble model simulations. The model simulates in situ parameters that were assimilated (net primary production and gravitational particle flux) and parameters that were withheld (234Thorium and nitrogen isotopes) with reasonable accuracy. Model results show that gravitational flux of sinking particles and vertical mixing of organic matter from the euphotic zone are more important biological pump pathways than active transport by vertically migrating zooplankton. However, these processes are regionally variable, with sinking particles most important in oligotrophic areas of the Gulf of Mexico and California Current, sinking particles and vertical mixing roughly equivalent in productive coastal upwelling regions and the subtropical front in the Southern Ocean, and active transport an important contributor in the eastern tropical Pacific. We further find that mortality at depth is an important component of active transport when mesozooplankton biomass is high, but it is negligible in regions with low mesozooplankton biomass. Our results also highlight the high degree of uncertainty, particularly amongst mesozooplankton functional groups, that is derived from uncertainty in model parameters. Indeed, variability in BCP pathways between simulations for a specific location using different parameter sets (all with approximately equal misfit relative to observations) is comparable to variability in BCP pathways between regions. We discuss the implications of these results for other data-assimilation approaches and for studies that rely on non-ensemble model outputs.

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Bogorad, Max I., and Peter C. Searson. "Real-time imaging and quantitative analysis of doxorubicin transport in a perfusable microvessel platform." Integrative Biology 8, no. 9 (2016): 976–84. http://dx.doi.org/10.1039/c6ib00082g.

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The kinetics of solute transport across cell monolayers is complex, and often consists of multiple active transport processes in addition to passive diffusion. Here we demonstrate that mechanistic details of transport across biological barriers can be obtained from live cell imaging in a perfusable microvessel model with physiologically relevant geometry.

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Halpin, Patricia A., and Chaya Gopalan. "Teaching Membrane Transport Concepts Using Flipped Teaching & Dramatizations." American Biology Teacher 83, no. 5 (May 1, 2021): 337–40. http://dx.doi.org/10.1525/abt.2021.83.5.337.

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Cell membrane transport is an important topic discussed in the biology classroom from the middle school to the graduate level. Membrane transport is complex, and students are often confused between different types of transport mechanisms. Dramatization is an active-learning strategy to engage students in learning. The flipped teaching method is designed to introduce lecture content prior to class meeting, thus creating time during class to adapt active-learning strategies such as dramatization. In this work, students were given a pretest prior to the dramatization activity. As each type of membrane transport was discussed, which included simple diffusion, osmosis, facilitated diffusion, and active transport, students were assigned specific roles to demonstrate the movement. The dramatization activity triggered many questions related to the topic, and these questions were addressed immediately. A posttest was conducted at the end of the dramatization activity. Our results demonstrated increases in the students’ understanding, engagement, and confidence level. The combination of flipped teaching and dramatization thus serves as a student-centered active-learning strategy for teaching difficult biological concepts.

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Kumar, Manish, Jeffrey S. Guasto, and Arezoo M. Ardekani. "Transport of complex and active fluids in porous media." Journal of Rheology 66, no. 2 (March 2022): 375–97. http://dx.doi.org/10.1122/8.0000389.

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Complex and active fluids find broad applications in flows through porous materials. Nontrivial rheology can couple to porous microstructure leading to surprising flow patterns and associated transport properties in geophysical, biological, and industrial systems. Viscoelastic instabilities are highly sensitive to pore geometry and can give rise to chaotic velocity fluctuations. A number of recent studies have begun to untangle how the pore-scale geometry influences the sample-scale flow topology and the resulting dispersive transport properties of these complex systems. Beyond classical rheological properties, active colloids and swimming cells exhibit a range of unique properties, including reduced effective viscosity, collective motion, and random walks, that present novel challenges to understanding their mechanics and transport in porous media flows. This review article aims to provide a brief overview of essential, fundamental concepts followed by an in-depth summary of recent developments in this rapidly evolving field. The chosen topics are motivated by applications, and new opportunities for discovery are highlighted.

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Feng, Yaning, Enhe Bayaer, and Yanhua Qi. "Advances in the Biological Functions of Auxin Transporters in Rice." Agriculture 12, no. 7 (July 9, 2022): 989. http://dx.doi.org/10.3390/agriculture12070989.

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Auxin is the earliest discovered plant hormone, which plays important roles in each aspect of plant growth and development. There are two main pathways for auxin to be transported from the synthetic site (such as young leaves and terminal buds) to the active site. First, auxin is transported over long distances through phloem in an unfixed direction throughout the whole plant. Second, short-distance polar transport between cells requires the participation of auxin carriers, including unidirectional transport from stem tip to root and local unidirectional transport between tissues. Polar transport is critical to the establishment and maintenance of the auxin concentration gradient, which specifically regulates plant growth and development and responds to environmental changes. In this article, we reviewed the research progress of auxin transporters AUX1/LAX, PIN, and ABCB families, and some potential auxin transporters in rice growth and development, which provide information for the interpretation of biological functions of polar auxin transport families and lay a foundation for the genetic improvement of important agronomic traits in rice.

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Varela, Manuel F., Anely Ortiz-Alegria, Manjusha Lekshmi, Jerusha Stephen, and Sanath Kumar. "Functional Roles of the Conserved Amino Acid Sequence Motif C, the Antiporter Motif, in Membrane Transporters of the Major Facilitator Superfamily." Biology 12, no. 10 (October 16, 2023): 1336. http://dx.doi.org/10.3390/biology12101336.

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The biological membrane surrounding all living cells forms a hydrophobic barrier to the passage of biologically important molecules. Integral membrane proteins called transporters circumvent the cellular barrier and transport molecules across the cell membrane. These molecular transporters enable the uptake and exit of molecules for cell growth and homeostasis. One important collection of related transporters is the major facilitator superfamily (MFS). This large group of proteins harbors passive and secondary active transporters. The transporters of the MFS consist of uniporters, symporters, and antiporters, which share similarities in structures, predicted mechanism of transport, and highly conserved amino acid sequence motifs. In particular, the antiporter motif, called motif C, is found primarily in antiporters of the MFS. The antiporter motif’s molecular elements mediate conformational changes and other molecular physiological roles during substrate transport across the membrane. This review article traces the history of the antiporter motif. It summarizes the physiological evidence reported that supports these biological roles.

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Liao, Xiaomei, Yan Du, Tianyu Wang, Shuibo Hu, Haigang Zhan, Huizeng Liu, and Guofeng Wu. "High-Frequency Variations in Pearl River Plume Observed by Soil Moisture Active Passive Sea Surface Salinity." Remote Sensing 12, no. 3 (February 8, 2020): 563. http://dx.doi.org/10.3390/rs12030563.

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River plumes play an important role in the cross-margin transport of phytoplankton and nutrients, which have profound impacts on coastal ecosystems. Using recently available Soil Moisture Active Passive (SMAP) sea surface salinity (SSS) data and high-resolution ocean color products, this study investigated summertime high-frequency variations in the Pearl River plume of China and its biological response. The SMAP SSS captures the intraseasonal oscillations in the offshore transport of the Pearl River plume well, which has distinct 30–60 day variations from mid-May to late September. The offshore transport of freshwater varies concurrently with southwesterly wind anomalies and is roughly in phase with the Madden–Julian Oscillation (MJO) index in phases 1–5, thus implying that the MJO exerts a significant influence. During MJO phases 1–2, the southwest wind anomalies in the northeastern South China Sea (SCS) enhanced cross-shore Ekman transport, while the northeast wind anomalies during MJO phases 3–5 favored the subsequent southwestward transport of the plume. The high chlorophyll-a concentration coincided well with the low-salinity water variations, emphasizing the important role of the offshore transport of the Pearl River plume in sustaining biological production over the oligotrophic northern SCS. The strong offshore transport of the plume in June 2015 clearly revealed that the proximity of a cyclonic eddy plays a role in the plume’s dispersal pathway. In addition, heavy rainfall related to the landfall of tropical cyclones in the Pearl River Estuary region contributed to the episodic offshore transport of the plume.

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Collis, J., D. L. Brown, M. E. Hubbard, and R. D. O’Dea. "Effective equations governing an active poroelastic medium." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2198 (February 2017): 20160755. http://dx.doi.org/10.1098/rspa.2016.0755.

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In this work, we consider the spatial homogenization of a coupled transport and fluid–structure interaction model, to the end of deriving a system of effective equations describing the flow, elastic deformation and transport in an active poroelastic medium. The ‘active’ nature of the material results from a morphoelastic response to a chemical stimulant, in which the growth time scale is strongly separated from other elastic time scales. The resulting effective model is broadly relevant to the study of biological tissue growth, geophysical flows (e.g. swelling in coals and clays) and a wide range of industrial applications (e.g. absorbant hygiene products). The key contribution of this work is the derivation of a system of homogenized partial differential equations describing macroscale growth, coupled to transport of solute, that explicitly incorporates details of the structure and dynamics of the microscopic system, and, moreover, admits finite growth and deformation at the pore scale. The resulting macroscale model comprises a Biot-type system, augmented with additional terms pertaining to growth, coupled to an advection–reaction–diffusion equation. The resultant system of effective equations is then compared with other recent models under a selection of appropriate simplifying asymptotic limits.

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Ma, Zhichao, Yinning Zhou, Feiyan Cai, Long Meng, Hairong Zheng, and Ye Ai. "Ultrasonic microstreaming for complex-trajectory transport and rotation of single particles and cells." Lab on a Chip 20, no. 16 (2020): 2947–53. http://dx.doi.org/10.1039/d0lc00595a.

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We present a versatile ultrasonic microstreaming based manipulation method that enables active and precise control of transport and rotation of individual microscale particles and biological cells in microfluidics.

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Wang, B., W. Wang, J. Jiang, and C. E. Ballard. "Prodrug Approaches to the Improved Delivery of Peptide Drugs." Current Pharmaceutical Design 5, no. 4 (April 1999): 265–87. http://dx.doi.org/10.2174/1381612805666230109214307.

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Undesirable pharmaceutical and biopharmaceutical properties, which include low water solubility, poor stability, and low permeability through biological membrane barriers, often hinder the clinical development of biologically active peptides. Finding solutions to these problems is a contemporary issue in developing clinically the vast number of biologically active peptides as drugs. In recent years, significant progress has been made in developing prodrug approaches for the improvement of the water solubility, stability, and membrane permeability of peptides. For improving water solubility, the focus has been on the bioreversible introduction of ionizable functional groups to peptides, which helps to increase the polarity and thus water solubility of the peptide drugs. For improving stability, efforts have focused on stabilizing peptides against exopeptit.lase-mediated hydrolysis by bioreversibly masking the terminal carboxyl and/or amino groups. For improving permeability through biological barriers, recent efforts have focused on both improving the lipophilicity of a peptide in order to facilitate its passive permeation through biological membranes and conjugation of a peptide to a carrier which allows for the active transport of the peptide-carrier conjugate. Many of the prodrug systems developed recently have the potential to be used clinically for the delivery of peptide drugs to the desired site of action.

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McWhorter, Todd J., Bradley Hartman Bakken, William H. Karasov, and Carlos Martínez del Rio. "Hummingbirds rely on both paracellular and carrier-mediated intestinal glucose absorption to fuel high metabolism." Biology Letters 2, no. 1 (September 27, 2005): 131–34. http://dx.doi.org/10.1098/rsbl.2005.0388.

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Twenty years ago, the highest active glucose transport rate and lowest passive glucose permeability in vertebrates were reported in Rufous and Anna's hummingbirds ( Selasphorus rufus , Calypte anna ). These first measurements of intestinal nutrient absorption in nectarivores provided an unprecedented physiological foundation for understanding their foraging ecology. They showed that physiological processes are determinants of feeding behaviour. The conclusion that active, mediated transport accounts for essentially all glucose absorption in hummingbirds influenced two decades of subsequent research on the digestive physiology and nutritional ecology of nectarivores. Here, we report new findings demonstrating that the passive permeability of hummingbird intestines to glucose is much higher than previously reported, suggesting that not all sugar uptake is mediated. Even while possessing the highest active glucose transport rates measured in vertebrates, hummingbirds must rely partially on passive non-mediated intestinal nutrient absorption to meet their high mass-specific metabolic demands.

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DeLuca, H. F., R. R. Sicinski, Y. Tanaka, P. H. Stern, and C. M. Smith. "Biological activity of 1,25-dihydroxyvitamin D2 and 24-epi-1,25-dihydroxyvitamin D2." American Journal of Physiology-Endocrinology and Metabolism 254, no. 4 (April 1, 1988): E402—E406. http://dx.doi.org/10.1152/ajpendo.1988.254.4.e402.

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The biological activity of 1,25-dihydroxyvitamin D2 [1,25(OH)2D2] and 24-epi-1,25-dihydroxyvitamin D2 [24-epi-1,25(OH)2D2] has been determined in vitamin D-deficient rats. The biological effectiveness of 1,25(OH)2D2 is equal to that reported previously for 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] (15) in intestinal calcium transport, mineralization of bone, mobilization of bone calcium, and elevation of plasma inorganic phosphorus of rachitic rats. However, 24-epi-1,25(OH)2D2 is at best one-half as active as 1,25(OH)2D2 in stimulating intestinal calcium transport and in the mineralization of rachitic bone. The 24-epi-1,25(OH)2D2 is one-third as active as 1,25(OH)2D3 in binding to the chick intestinal receptor for 1,25(OH)2D3. Thus receptor discrimination may account for the twofold difference in intestinal calcium transport activity. 24-Epi-1,25(OH)2D2 appeared inactive in in vivo mobilization of bone calcium or bone phosphorus. On the other hand, in fetal rat bone in culture, the epi compound was only five times less active than 1,25(OH)2D2 in inducing resorption. Short-term experiments on bone mineral mobilization in vivo show that the 24-epi-1,25(OH)2D2 does induce bone calcium mobilization but that its activity in this respect is short lived. It is suggested that 24-epi-1,25(OH)2D2 and, as a result, it shows preferential activity on intestine whose response to a single dose of 1,25(OH)2D2 remains for several days, whereas the short-lived bone system does not remain stimulated during the 24-h period between doses.

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Dora, M., and D. Holcman. "Active flow network generates molecular transport by packets: case of the endoplasmic reticulum." Proceedings of the Royal Society B: Biological Sciences 287, no. 1930 (July 2020): 20200493. http://dx.doi.org/10.1098/rspb.2020.0493.

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Biological networks are characterized by their connectivity and topology but also by their ability to transport materials. In the case of random transportation, the efficacy is measured by the time it takes to travel between two nodes of the network. We study here the consequences of a unidirectional transport mechanism occurring in the endoplasmic reticulum (ER) network, a structure present in the cell cytoplasm. This unidirectional transport mechanism is an active-waiting transportation, where molecules have to wait a random time before being transported from one node to the next one. We develop here a general theory of transport in an active network and find an unusual network transportation, where molecules group together in redundant packets instead of being disperse. Finally, the mean time to travel between two nodes of the ER is of the order of 20 min, but is reduced to 30 s when we consider the fastest particles because it uses optimal paths. To conclude, the present theory shows that unidirectional transport is an efficient and robust mechanism for fast molecular redistribution inside the ER.

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Woodhouse, Francis G., Aden Forrow, Joanna B. Fawcett, and Jörn Dunkel. "Stochastic cycle selection in active flow networks." Proceedings of the National Academy of Sciences 113, no. 29 (July 5, 2016): 8200–8205. http://dx.doi.org/10.1073/pnas.1603351113.

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Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such nonequilibrium networks. Here we connect concepts from lattice field theory, graph theory, and transition rate theory to understand how topology controls dynamics in a generic model for actively driven flow on a network. Our combined theoretical and numerical analysis identifies symmetry-based rules that make it possible to classify and predict the selection statistics of complex flow cycles from the network topology. The conceptual framework developed here is applicable to a broad class of biological and nonbiological far-from-equilibrium networks, including actively controlled information flows, and establishes a correspondence between active flow networks and generalized ice-type models.

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Bulmus, Volga. "Biomembrane-Active Molecular Switches as Tools for Intracellular Drug Delivery." Australian Journal of Chemistry 58, no. 6 (2005): 411. http://dx.doi.org/10.1071/ch05066.

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Many therapeutic strategies, such as gene therapy and vaccine development require the delivery of polar macromolecules (e.g. DNA, RNA, and proteins) to intracellular sites at a therapeutic concentration. For such macromolecular therapeutics, cellular membranes constitute a major transport barrier that must be overcome before these drugs can exert their biological activity inside cells. A number of biological organisms, e.g. viruses and toxins, efficiently destabilize the cellular membranes upon a trigger, such as low pH, and facilitate the delivery of their biological cargo to the cytoplasm of host cell. pH-responsive synthetic peptides and polymers have been designed to mimic the function of membrane-destabilizing natural organisms and evaluated as a part of drug delivery systems. In this Review, pH-dependent membrane activity of natural and synthetic systems is reviewed, focussing on fundamental and practical aspects of pH-responsive, membrane-disruptive synthetic polymers in intracellular drug delivery.

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Ha, Yeonjeong, Xianzhe Wang, Howard M. Liljestrand, Jennifer A. Maynard, and Lynn E. Katz. "Elucidating the mechanism of cellular uptake of fullerene nanoparticles." Environmental Engineering Research 27, no. 2 (March 3, 2021): 200658–0. http://dx.doi.org/10.4491/eer.2020.658.

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Understanding the molecular interactions between biological cells and engineered nanoparticles is a key to evaluating potential toxicities to humans and the environment. This study developed a method to determine the mechanisms by which fullerene aggregates are distributed into a representative cell line, human intestinal Caco-2 cells. First, we determined that the presence of fetal bovine serum (FBS) in the cell culture media changes the particle characteristics and inhibits particle adsorptions onto cell surfaces. Second, significantly lower amounts of fullerene were internalized at 4°C, a temperature at which active transport mechanisms are effectively impeded, than at 37°C. Third, metabolic inhibitors of active transport and a microtubule transport inhibitor decreased fullerene uptake at 37°C. Fourth, cellular uptake of fullerene increased with increasing fullerene concentration, suggesting that passive diffusion into lipid membranes contributed to uptake over the broad concentration range used in this study. Together, these results indicate fullerene transport into cells occurs via two mechanisms: passive diffusion across the lipid bilayer and active transport including microtubule involved endocytosis. The results also suggest that simple physical-chemical partitioning models do not fully describe fullerene uptake, and instead, active transport models are also required to estimate the cellular uptake and toxicity of fullerene.

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Bowry, Sudhir K., Fatih Kircelli, Mooppil Nandakumar, and Tushar J. Vachharajani. "Clinical relevance of abstruse transport phenomena in haemodialysis." Clinical Kidney Journal 14, Supplement_4 (December 2021): i85—i97. http://dx.doi.org/10.1093/ckj/sfab183.

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ABSTRACT Haemodialysis (HD) utilizes the bidirectional properties of semipermeable membranes to remove uraemic toxins from blood while simultaneously replenishing electrolytes and buffers to correct metabolic acidosis. However, the nonspecific size-dependent transport across membranes also means that certain useful plasma constituents may be removed from the patient (together with uraemic toxins), or toxic compounds, e.g. endotoxin fragments, may accompany electrolytes and buffers of the dialysis fluids into blood and elicit severe biological reactions. We describe the mechanisms and implications of these undesirable transport processes that are inherent to all HD therapies and propose approaches to mitigate the effects of such transport. We focus particularly on two undesirable events that are considered to adversely affect HD therapy and possibly impact patient outcomes. Firstly, we describe how loss of albumin (and other essential substances) can occur while striving to eliminate larger uraemic toxins during HD and why hypoalbuminemia is a clinical condition to contend with. Secondly, we describe the origins and mode of transport of biologically active substances (from dialysis fluids with bacterial contamination) into the blood compartment and biological reactions they elicit. Endotoxin fragments activate various proinflammatory pathways to increase the underlying inflammation associated with chronic kidney disease. Both phenomena involve the physical as well as chemical properties of membranes that must be selected judiciously to balance the benefits with potential risks patients may encounter, in both the short and long term.

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Sviridov, O. V. "Proteins binding the thyroid hormones and their physiological role." Problems of Endocrinology 40, no. 6 (December 15, 1994): 57–63. http://dx.doi.org/10.14341/probl12197.

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Steroid and thyroid hormones exert a regulatory effect on a whole range of physiological processes that form the basis of the normal development and functioning of the body. In the channel of human blood, from 96 to 99.9% of the total masses of cortisol, progesterone, thyroxine and triiodothyronine circulate in the form of complexes with hormone-binding transport proteins. The free hormone" hypothesis assigns to these transport proteins the passive function of maintaining a stationary pool of biologically active unbound hormones due to the rapid dissociation of complexes in response to the needs of target tissues. Recent studies have revealed the active role of transport proteins and their receptors on the surface of cell membranes in the interaction of steroid and thyroid hormones with competent tissues. The structural aspects of the biological activity of complexes of corticosteroid-binding and sex steroid-binding globulins with natural ligands are described in detail in a review article. This literature review is devoted to the description of the physicochemical properties and biomedical characteristics of a multicomponent system of proteins that bind thyroid hormones in human blood plasma. Particular attention is paid to the physiological significance of these proteins in the framework of the hypothesis of free hormones and in the light of their recently discovered specific transport functions.

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Kumar, R. "Vitamin D metabolism and mechanisms of calcium transport." Journal of the American Society of Nephrology 1, no. 1 (July 1990): 30–42. http://dx.doi.org/10.1681/asn.v1130.

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Vitamin D3 undergoes sequential hydroxylations in the liver and kidney to form 1,25-dihydroxyvitamin D3, the biologically active form of the vitamin. 1,25-dihydroxyvitamin D3 is metabolized by several processes in various target tissues that decrease the biological activity of the sterol. In addition, 1,25-dihydroxyvitamin D3 is excreted in the bile as polar metabolites, such as glucuronides and, possibly sulfates and neutral polar steroids. These compounds undergo an enterohepatic recirculation in both man and experimental animals. 1,25-dihydroxyvitamin D3 increases the absorption of calcium in the intestine and the reabsorption of calcium in the kidney. It induces the synthesis of several proteins, the most notable of which is calcium binding protein that is thought to play a role in the absorption of calcium. The vitamin D-dependent calcium binding proteins and the calcium-magnesium ATPase calcium pump are co-localized in several tissues that play a role in the absorption of calcium.

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Bisha, Ina, and Alessandra Magistrato. "The molecular mechanism of secondary sodium symporters elucidated through the lens of the computational microscope." RSC Advances 6, no. 12 (2016): 9522–40. http://dx.doi.org/10.1039/c5ra22131e.

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Transport of molecules across cellular membranes is a key biological process for normal cell function. In this review we describe current state-of-the-art knowledge on molecular mechanism of secondary active transporters obtained by molecular simulations studies.

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Schornack, P. A., S. K. Song, C. S. Ling, R. Hotchkiss, and J. J. Ackerman. "Quantification of ion transport in perfused rat heart: 133Cs+ as an NMR active K+ analog." American Journal of Physiology-Cell Physiology 272, no. 5 (May 1, 1997): C1618—C1634. http://dx.doi.org/10.1152/ajpcell.1997.272.5.c1618.

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Proper ion balance between intra- and extracellular compartments is necessary for normal physiological function. Conversely, alterations in membrane ion transport occur in numerous pathological states. As a noninvasive, nondestructive spectroscopic technique, nuclear magnetic resonance (NMR) offers a powerful approach to the study of ion balance in intact biological systems. Unfortunately, rare NMR active nuclides that are isotopes of the 100% naturally abundant 23Na+ and 39K+ are not available for tracer kinetic studies of Na1 and K+ transport. However, Cs is a biologically active analog of K+, and the 100% naturally abundant NMR active 133Cs+ nuclide can be employed to examine K+ transport (Davis, D. G., E. Murphy, and R. E. London. Biochemistry 27: 3547-3551, 1988). The distinguishing feature of 133Cs+ is that it naturally gives two separate well-resolved NMR resonances for intra- and extra-cellular 133Cs+, permitting study of the time course changes of either of these compartments independent of the other. In this report, the experimental procedures and compartmental modeling formalism are developed that allow quantitative analysis of Cs+ membrane transport in the perfused rat heart. Intracellular 133Cs+ is shown to be 100% visible by solution-state NMR methods and its influx transport to be markedly inhibited by ouabain, a confirmation of findings previously reported by others. Intracellular 133Cs+ spin-lattice and spin-spin relaxation times at 7 T were determined to be 2.1 +/- 0.3 (SD)s (n = 8) and 0.065 +/- 0.007 (SD) s (n = 8), respectively, for T1 and T2. The rate constant for Na(+)-K(+)-ATPase pump dominated intracellular influx was measured to be 0.25 +/- 0.07 (SD) min-1 (n = 27) and that for efflux 0.005 +/- 0.001 (SD) min-1 (n = 14). The rate constant for 133Cs+ equilibration in the extracellular space at supraphysiological perfusate flow rate (20 ml/min) was found to be 4.6 +/- 0.9 (SD) min-1 (n = 20). Thus extracellular diffusion limitations do not dominate the 133Cs+ transport measurements.

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Anguige, Keith, and Matthias Röger. "Global existence for a bulk/surface model for active-transport-induced polarisation in biological cells." Journal of Mathematical Analysis and Applications 448, no. 1 (April 2017): 213–44. http://dx.doi.org/10.1016/j.jmaa.2016.10.072.

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Valevski, Avi, Ilan Modal, Zohara Jerushalmy, Leonid Kikinzon, and Abraham Weizman. "Effect of melatonin on active transport of serotonin into blood platelets." Psychiatry Research 57, no. 2 (July 1995): 193–96. http://dx.doi.org/10.1016/0165-1781(95)02642-a.

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Harrison, Elizabeth. "Role-Playing Activity to Demonstrate the Electron Transport Chain." American Biology Teacher 82, no. 5 (May 1, 2020): 338–40. http://dx.doi.org/10.1525/abt.2020.82.5.338.

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The role of the electron transport chain, its associated proteins, and carrier molecules can be difficult for introductory biology students to understand. Role-playing activities provide a simple, active, cost-effective method for demonstrating and comprehending complex biological processes. This role-playing activity was designed to help introductory biology students learn the role of the electron transport chain in the synthesis of ATP. The activity can be completed within a single class period and, when combined with a post-activity writing assignment, can enhance student understanding of how the electron transport chain functions.

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Ndubuisi, MacKevin I., Kirit Patel, Ravi J. Rayanade, Abraham Mittelman, Lester T. May, and Pravin B. Sehgal. "Distinct Classes of Chaperoned IL-6 in Human Blood: Differential Immunological and Biological Availability." Journal of Immunology 160, no. 1 (January 1, 1998): 494–501. http://dx.doi.org/10.4049/jimmunol.160.1.494.

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Abstract Transport of IL-6 in blood is fundamental to the biology of this cytokine. In the present study, IL-6 transport, immunological reactivity, and biological availability were investigated in blood from melanoma patients subjected to different active specific immunization regimens (an anti-idiotypic mAb immunization protocol (mAb-keyhole limpet hemocyanin (KLH)-Calmette-Guérin bacillus (BCG), an autologous anti-cancer vaccine protocol (AAAP), or both). Sera were subjected to Sephadex G-200 gel filtration chromatography, and the structure and biological activity of IL-6 complexes in the eluate fractions were probed using five IL-6 ELISAs and two bioassays. Sera from patients administered mAb-KLH+BCG followed by AAAP contained three distinct classes of IL-6 eluting at 30, 200, and 450 kDa, each with its characteristic ELISA reactivity and bioactivity: the 30- and 450-kDa complexes were bioactive in the B9 and Hep3B assays, but the 200-kDa complex was not. The 30- and 450-kDa IL-6 complexes were preferentially reactive in the 7IL6/5IL6 ELISA, the 200-kDa IL-6 complexes were preferentially reactive in the 4IL6/5IL6 ELISA, while the three commercial ELISAs (R&D, Endogen, and Genzyme) detected essentially only the 30-kDa IL-6. In contrast, 1) sera from AAAP patients contained biologically active 30- and 450-kDa IL-6 complexes, while 2) sera from mAb-KLH+BCG patients contained 200-kDa IL-6 complexes inactive in ex vivo bioassays. Both the 450- and 200-kDa complexes included soluble IL-6R, with the 200-kDa complexes additionally containing ligand-occupied anti-IL-6 and anti-soluble IL-6R IgG. The data indicate the existence of specific mechanisms that regulate the transport and function of IL-6 in vivo.

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Fernández-Moreira, Vanesa, Raquel P. Herrera, and M. Concepción Gimeno. "Anticancer properties of gold complexes with biologically relevant ligands." Pure and Applied Chemistry 91, no. 2 (February 25, 2019): 247–69. http://dx.doi.org/10.1515/pac-2018-0901.

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Abstract The present review highlights our findings in the field of antitumor gold complexes bearing biologically relevant molecules, such as DNA-bases, amino acids or peptide derivatives. The results show that very active complexes are achieved with this sort of ligands in several cancer cells. In these compounds the gold center is bonded to these biological molecules mainly through a sulfur atom belonging to a cysteine moiety or to a thionicotinic moiety as result of the functionalization of the biological compounds, and additionally phosphines or N-heterocyclic carbenes are present as ancillary ligands. These robust compounds are stable in the biological media and can be transported to their targets without previous deactivation. The presence of these scaffolds represents a good approach to obtain complexes with improved biologically activity, better transport and biodistribution to cancer cells. Thioredoxin reductase (TrxR) has been shown as the main target for these complexes and in some cases, DNA interactions has been also observed.

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Larsen, Erik Hviid. "Hans Henriksen Ussing. 30 December 1911 — 22 December 2000." Biographical Memoirs of Fellows of the Royal Society 55 (January 2009): 305–35. http://dx.doi.org/10.1098/rsbm.2009.0002.

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Hans Ussing was born on 30 December 1911 at Sorø Academy in Denmark, where his father Dr Henrik Ussing was a lecturer and, as historian, a leading Danish folklorist. After his doctoral thesis in marine biology, Hans Ussing came to August Krogh's laboratory, where he studied protein turnover by using deuterium-labelled amino acids. After World War II, when radioactive isotopes of light elements became available for biological research, Ussing pioneered the development of epithelial physiology by introducing new concepts and theoretical tools, such as unidirectional fluxes, exchange diffusion, the flux-ratio equation, the shortcircuiting technique, solvent drag, anomalous solvent drag and the pre-steady-state flux ratio theorem. In studies on frog skin, combining electrophysiology and radioactive tracer technology, he provided the first unambiguous demonstration of active transport of sodium ions. His two-membrane hypothesis of active transport by frog skin initiated studies of epithelial transport at the cellular level in other organs and of the mechanisms of action of hormones and drugs. His discovery of paracellular ion transports bridged the physiology of high-resistance and low-resistance epithelia. With the Na + recirculation theory of isotonic transport he continued his studies of epithelial physiology until shortly before his death. Ussing's scientific research provided analytical methods and new insights of general applicability for the study of absorbing and secreting epithelia—of equal importance to biology and medicine. Hans Ussing died on 22 December 2000 after a short illness.

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Beckstein, Oliver, and Fiona Naughton. "General principles of secondary active transporter function." Biophysics Reviews 3, no. 1 (March 2022): 011307. http://dx.doi.org/10.1063/5.0047967.

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Transport of ions and small molecules across the cell membrane against electrochemical gradients is catalyzed by integral membrane proteins that use a source of free energy to drive the energetically uphill flux of the transported substrate. Secondary active transporters couple the spontaneous influx of a “driving” ion such as Na+ or H+ to the flux of the substrate. The thermodynamics of such cyclical non-equilibrium systems are well understood, and recent work has focused on the molecular mechanism of secondary active transport. The fact that these transporters change their conformation between an inward-facing and outward-facing conformation in a cyclical fashion, called the alternating access model, is broadly recognized as the molecular framework in which to describe transporter function. However, only with the advent of high resolution crystal structures and detailed computer simulations, it has become possible to recognize common molecular-level principles between disparate transporter families. Inverted repeat symmetry in secondary active transporters has shed light onto how protein structures can encode a bi-stable two-state system. Based on structural data, three broad classes of alternating access transitions have been described as rocker-switch, rocking-bundle, and elevator mechanisms. More detailed analysis indicates that transporters can be understood as gated pores with at least two coupled gates. These gates are not just a convenient cartoon element to illustrate a putative mechanism but map to distinct parts of the transporter protein. Enumerating all distinct gate states naturally includes occluded states in the alternating access picture and also suggests what kind of protein conformations might be observable. By connecting the possible conformational states and ion/substrate bound states in a kinetic model, a unified picture emerges in which the symporter, antiporter, and uniporter functions are extremes in a continuum of functionality. As usual with biological systems, few principles and rules are absolute and exceptions are discussed as well as how biological complexity may be integrated in quantitative kinetic models that may provide a bridge from the structure to function.

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Vorobyev, Sergei I., Sergey B. Bolevich, Sergey V. Votrin, Aleksandra S. Orlova, Alexey A. Novikov, Stefani S. Bolevich, Dmitrii V. Gudanovich, et al. "Hemocorrectors Based on Perfluorocarbon Gas-Transport Blood-Substituting Emulsions." Serbian Journal of Experimental and Clinical Research 22, no. 2 (June 1, 2021): 95–100. http://dx.doi.org/10.2478/sjecr-2021-0031.

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Abstract Hemocorrectors based on perfluorocarbon gas-transport blood-substituting emulsions are complex multiphase systems used in the biomedical field as multifunctional drugs, in particular, as gas-transport substitutes for a blood donor. The aim of this review was to discuss their physicochemical and medico-biological properties. A number of preparations from both Russian and foreign manufacturers based on chemically inert perfluorocarbon blood-substituting emulsions of a nano-size level as hemocorrectors with a gas transport function are shown. The analysis of the effect of perfluorocarbon emulsion on the blood gas transport indicators showed that perfluorocarbon particles in the bloodstream will significantly improve the conditions of gas exchange in tissues. The most important issue is the concentration of perfluorocarbon blood-substituting emulsions. The perfluorocarbon emulsions can be considered as a means of correcting the gas transport properties of blood, increasing the reserve capacity of blood cells-red blood cells to deliver oxygen to the tissues. Taking into account all facts about perfluorocarbon hemocorrectors, it can be concluded that they can be used as universal nanocarriers for the transdermal delivery of oxygen and biologically active compounds in various fields of biomedicine and cosmetology.

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Díaz-Galindo, Edaena Pamela, Aleksandra Nesic, Silvia Bautista-Baños, Octavio Dublan García, and Gustavo Cabrera-Barjas. "Corn-Starch-Based Materials Incorporated with Cinnamon Oil Emulsion: Physico-Chemical Characterization and Biological Activity." Foods 9, no. 4 (April 10, 2020): 475. http://dx.doi.org/10.3390/foods9040475.

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Active packaging represents a large and diverse group of materials, with its main role being to prolong the shelf-life of food products. In this work, active biomaterials based on thermoplastic starch-containing cinnamon oil emulsions were prepared by the compression molding technique. The thermal, mechanical, and antifungal properties of obtained materials were evaluated. The results showed that the encapsulation of cinnamon oil emulsions did not influence the thermal stability of materials. Mechanical resistance to break was reduced by 27.4%, while elongation at break was increased by 44.0% by the addition of cinnamon oil emulsion. Moreover, the novel material provided a decrease in the growth rate of Botrytis cinerea by 66%, suggesting potential application in food packaging as an active biomaterial layer to hinder further contamination of fruits during the storage and transport period.

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Knöpfel, Thomas, Nina Himmerkus, Dorothee Günzel, Markus Bleich, Nati Hernando, and Carsten A. Wagner. "Paracellular transport of phosphate along the intestine." American Journal of Physiology-Gastrointestinal and Liver Physiology 317, no. 2 (August 1, 2019): G233—G241. http://dx.doi.org/10.1152/ajpgi.00032.2019.

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Inorganic phosphate (Pi) is crucial for many biological functions, such as energy metabolism, signal transduction, and pH buffering. Efficient systems must exist to ensure sufficient supply for the body of Pi from diet. Previous experiments in humans and rodents suggest that two pathways for the absorption of Pi exist, an active transcellular Pi transport and a second paracellular pathway. Whereas the identity, role, and regulation of active Pi transport have been extensively studied, much less is known about the properties of the paracellular pathway. In Ussing chamber experiments, we characterized paracellular intestinal Pi permeabilities and fluxes. Dilution potential measurements in intestinal cell culture models demonstrated that the tight junction is permeable to Pi, with monovalent Pi having a higher permeability than divalent Pi. These findings were confirmed in rat and mouse intestinal segments by use of Ussing chambers and a combination of dilution potential measurements and fluxes of radiolabeled 32Pi. Both techniques yielded very similar results, showing that paracellular Pi fluxes were bidirectional and that Pi permeability was ~50% of the permeability for Na+ or Cl−. Pi fluxes were a function of the concentration gradient and Pi species (mono- vs. divalent Pi). In mice lacking the active transcellular Pi transport component sodium-dependent Pi transporter NaPi-IIb, the paracellular pathway was not upregulated. In summary, the small and large intestines have a very high paracellular Pi permeability, which may favor monovalent Pi fluxes and allow efficient uptake of Pi even in the absence of active transcellular Pi uptake. NEW & NOTEWORTHY The paracellular permeability for phosphate is high along the entire axis of the small and large intestine. There is a slight preference for monovalent phosphate. Paracellular phosphate fluxes do not increase when transcellular phosphate transport is genetically abolished. Paracellular phosphate transport may be an important target for therapies aiming to reduce intestinal phosphate absorption.

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Venter, H., S. Shahi, L. Balakrishnan, S. Velamakanni, A. Bapna, B. Woebking, and H. W. van Veen. "Similarities between ATP-dependent and ion-coupled multidrug transporters." Biochemical Society Transactions 33, no. 5 (October 26, 2005): 1008–11. http://dx.doi.org/10.1042/bst0331008.

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The movement of drugs across biological membranes is mediated by two major classes of membrane transporters. Primary-active, ABC (ATP-binding cassette) multidrug transporters are dependent on ATP-binding/hydrolysis, whereas secondary-active multidrug transporters are coupled to the proton (or sodium)-motive force that exists across the plasma membrane. Recent work on LmrA, an ABC multidrug transporter in Lactococcus lactis, suggests that primary- and secondary-active multidrug transporters share functional and structural features. Some of these similarities and their implications for the mechanism of transport by ABC multidrug transporters will be discussed.

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Vlasov, Timur D., and Artemiy V. Rubinskiy. "Operation of “russian maglev” transport system and medical-biological safety aspects." Transportation systems and technology 3, no. 3 (September 15, 2017): 111–32. http://dx.doi.org/10.17816/transsyst201733111-132.

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The article deals with the analysis of medical and biological safety of the results of work on the design and model-laboratory experiments of “Russian maglev” transport system. Purpose. The purpose of the work is determination of location and level of field physical characteristics of national magnetic levitation system “Russian maglev”, development of scientifically justified preventive-sanitary suggestions and recommendations necessary for design and application of the systems for protection, control and monitoring of hazardous effects of non-radiation physical fields on passengers, personnel and transported cargo and ecology. Methodology. To achieve the set purpose a review of modern ideas on the influence of constant and low frequency magnetic fields on people was carried out, characteristics of main sources of EMF influence on people during “Russian maglev” technologies operation were studied and described. The obtained results were compared with technical documents on electromagnetic safety. Results. As a result of this work, hygienic requirements for absolute levels and length of unfavourable factors impact on railway transport were determined, which are not mentioned in the active Sanitary Regulations and Instructions. Considering this, recommendations for the most safety placement of MF for people and safety means in crew vehicle were given. Practical significance. The significance of this work is that the preliminary work for medical-biological studies in conditions of full-size model was carried out.

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S. Ol’shevskaya, Yuliya, Aleksandr S. Kozlov, Aleksandr K. Petrov, Tatyana A. Zapara, and Aleksandr S. Ratushnyak. "Cell Membrane Permeability Under the Influence of Terahertz (Submillimeter) Laser Radiation." Siberian Journal of Physics 5, no. 4 (December 1, 2010): 177–81. http://dx.doi.org/10.54362/1818-7919-2010-5-4-177-181.

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Within the framework of the task of revealing the mechanisms of the action of terahertz (submillimeter) radiation on biological objects, the influence of terahertz (submillimeter) radiation on the processes of transmembrane transport in cell systems was experimentally analyzed. Complex research using dyes which do not penetrate through intact membranes (Trypan Blue) and reveal viable cells (BCECF-AM) together with electrophysiological analysis has shown that radiation with a 130-micron wavelength creates conditions for penetration of compounds that usually do not go through the membrane of living cells. The penetration of dye may be conditioned by reversible disturbance in the barrier properties of neuron membranes under the action of 130-micron waves. Radiation with a wavelength of 150 microns does not show such properties. The received results may offer the challenge of developing methods of directed transport of biologically active compounds into cells

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Krndija, Denis, and Michael Fairhead. "IGF1R undergoes active and directed centripetal transport on filopodia upon receptor activation." Biochemical Journal 476, no. 23 (December 3, 2019): 3583–93. http://dx.doi.org/10.1042/bcj20190665.

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Filopodia are thin, actin-based membrane protrusions with roles in sensing external mechanical and chemical cues, such as growth factor gradients in tissues. It was proposed that the chemical sensing role of filopodia is achieved through clearance of activated signaling receptors from filopodia. Type I insulin-like growth factor receptor (IGF1R) is a key regulator of normal development and growth, as well as tumor development and progression. Its biological roles depend on its activation upon IGF1 binding at the cell membrane. IGF1R behavior at the cell membrane and in particular in filopodia, has not been established. We found that IGF1 activation led to a gradual reduction in IGF1R puncta in filopodia, and that this clearance depended on actin, non-muscle myosin II, and IGF1R kinase activity. Using single particle tracking of filopodial IGF1R, we established that ligand-free IGF1R undergoes non-directional unidimensional diffusion along the filopodium. Moreover, after initial diffusion, the ligand-bound IGF1R is actively transported along the filopodium towards the filopodium base, and consequently cleared from the filopodium. Our results show that IGF1R can move directionally on the plasma membrane protrusions, supporting a sensory role for filopodia in interpreting local IGF1 gradients.

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Journal articles on the topic 'Active biological transport'

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