The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ulrich S Schubert - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamic analysis resolves the pharmaceutically relevant absolute molar mass and solution properties of synthetic poly ethylene glycol s created by varying initiation sites
Analytical Chemistry, 2017Co-Authors: Ivo Nischang, Igor Perevyazko, Tobias C Majdanski, Jurgen Vitz, Grit Festag, Ulrich S SchubertAbstract:The solution behavior originating from molecular characteristics of synthetic Macromolecules plays a pivotal role in many areas, in particular the life sciences. This situation necessitates the use of complementary hydrodynamic analytical methods as the only means for a complete structural understanding of any macromolecule in solution. To this end, we present a combined hydrodynamic approach for studying in-house prepared, low dispersity poly(ethylene glycols)s (PEGs), also known as poly(ethylene oxide)s (PEOs) depending on the classification used, synthesized from varying initiation sites by the living anionic ring opening polymerization. The series of linear PEGs in the molar mass range of only a few thousand to 50 000 g mol–1 have been studied in detail via viscometry and sedimentation-diffusion analysis by analytical ultracentrifugation. The obtained estimations for intrinsic viscosity, diffusion coefficients, and sedimentation coefficients of the Macromolecules in the solution-based analysis clearly...
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Hydrodynamic Analysis Resolves the Pharmaceutically-Relevant Absolute Molar Mass and Solution Properties of Synthetic Poly(ethylene glycol)s Created by Varying Initiation Sites
2016Co-Authors: Ivo Nischang, Igor Perevyazko, Tobias C Majdanski, Jurgen Vitz, Grit Festag, Ulrich S SchubertAbstract:The solution behavior originating from molecular characteristics of synthetic Macromolecules plays a pivotal role in many areas, in particular the life sciences. This situation necessitates the use of complementary hydrodynamic analytical methods as the only means for a complete structural understanding of any macromolecule in solution. To this end, we present a combined hydrodynamic approach for studying in-house prepared, low dispersity poly(ethylene glycols)s (PEGs), also known as poly(ethylene oxide)s (PEOs) depending on the classification used, synthesized from varying initiation sites by the living anionic ring opening polymerization. The series of linear PEGs in the molar mass range of only a few thousand to 50 000 g mol–1 have been studied in detail via viscometry and sedimentation-diffusion analysis by analytical ultracentrifugation. The obtained estimations for intrinsic viscosity, diffusion coefficients, and sedimentation coefficients of the Macromolecules in the solution-based analysis clearly showed self-consistency of the followed hydrodynamic approach. This self-consistency is underpinned by appropriate and physically sound values of hydrodynamic invariants, indicating adequate values of derived absolute molar masses. The classical scaling relations of Kuhn–Mark–Houwink–Sakurada of all molar-mass dependent hydrodynamic estimates show linear trends, allowing for interrelation of all parametric macromolecular characteristics. Differences among these are ascribed to the observation of α-end and chain-length dependent solvation of the Macromolecules, identified from viscometric studies. This important information allows for analytical tracing of variations of scaling relationships and a physically sound estimation of hydrodynamic characteristics. The demonstrated self-sufficient methodology paves an important way for a complete structural understanding and potential replacement of pharmaceutically relevant PEGs by alternative Macromolecules offering a suite of similar or tractably distinct physicochemical properties
Mazin Magzoub - One of the best experts on this subject based on the ideXlab platform.
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enhanced macromolecule diffusion deep in tumors after enzymatic digestion of extracellular matrix collagen and its associated proteoglycan decorin
The FASEB Journal, 2008Co-Authors: Mazin MagzoubAbstract:Drug access to tumors is limited by diffusion through the tumor interstitium. We used a microfiberoptic epifluorescence photobleaching method to determine the role of extracellular matrix (ECM) components in macromolecule diffusion deep in tumor tissue. In subcutaneous B16 tumors in living mice, translational diffusion of 10 kDa FITC-dextran was slowed 2- to 3-fold (compared with its diffusion in water) within a depth of 0.2 mm from the tumor surface, but >10-fold beyond a depth of 1 mm. Diffusion of larger Macromolecules, FITC-albumin and 500 kDa FITC-dextran, was slowed by up to 40-fold at 0.5 mm and 300-fold at 2 mm. Intratumoral collagenase (to digest collagen) or cathespin C (to digest decorin) each increased diffusion of 10 kDa FITC-dextran by ∼2-fold. However, these treatments dramatically increased diffusion (>10-fold) of larger Macromolecules, such as 500 kDa dextran, in deep tumor (2 mm depth). Intratumoral hyaluronidase, in contrast, slowed diffusion throughout the tumor. In vitro measurements ...
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enhanced macromolecule diffusion deep in tumors after enzymatic digestion of extracellular matrix collagen and its associated proteoglycan decorin
The FASEB Journal, 2008Co-Authors: Mazin Magzoub, Songwan Jin, A S VerkmanAbstract:Drug access to tumors is limited by diffusion through the tumor interstitium. We used a microfiberoptic epifluorescence photobleaching method to determine the role of extracellular matrix (ECM) components in macromolecule diffusion deep in tumor tissue. In subcutaneous B16 tumors in living mice, translational diffusion of 10 kDa FITC-dextran was slowed 2- to 3-fold (compared with its diffusion in water) within a depth of 0.2 mm from the tumor surface, but >10-fold beyond a depth of 1 mm. Diffusion of larger Macromolecules, FITC-albumin and 500 kDa FITC-dextran, was slowed by up to 40-fold at 0.5 mm and 300-fold at 2 mm. Intratumoral collagenase (to digest collagen) or cathepsin C (to digest decorin) each increased diffusion of 10 kDa FITC-dextran by approximately 2-fold. However, these treatments dramatically increased diffusion (>10-fold) of larger Macromolecules, such as 500 kDa dextran, in deep tumor (2 mm depth). Intratumoral hyaluronidase, in contrast, slowed diffusion throughout the tumor. In vitro measurements in defined gel-like mixtures of collagen, hyaluronan, and decorin closely recapitulated results in tumors in vivo. Mathematical modeling quantified the roles of extracellular space volume fraction and dimensions, and indicated a substantial effect of cell density on diffusion in deep tumor. Our data define the determinants of diffusion in deep tumor and suggest collagen and decorin digestion to greatly facilitate macromolecule delivery.
Leandro Rodrigues De Lemos - One of the best experts on this subject based on the ideXlab platform.
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phase diagrams densities and refractive indexes of aqueous two phase systems comprising f68 l64 or peo1500 ammonium sodium or potassium thiocyanate salts water effect of cation and type of macromolecule
Journal of Chemical & Engineering Data, 2019Co-Authors: Maria C Hespanhol, Luis Henrique Mendes Da Silva, Beatriz M Fontoura, Vivianne Molica De Andrade, Aparecida Barbosa Mageste, Leandro Rodrigues De LemosAbstract:In extraction procedures, the more commonly used aqueous two-phase systems (ATPS) comprise mainly water, salt, and macromolecule, particularly the macromolecule poly(ethylene oxide) (PEO). However, one limitation of such ATPS is their capacity to separate compounds that are more hydrophobic. One possible solution to overcome this restriction is the use of ATPS formed with triblock copolymers, which are more hydrophobic and therefore enable the extraction of hydrophobic solutes. In addition, the range of applications of ATPS formed with thiocyanate salts can be broader, mainly to extract metal ions. In view of this, equilibrium data were acquired in this work by constructing phase diagrams for ATPS comprising Macromolecules [poly(ethylene oxide), PEO, or (poly(ethylene oxide))-(poly(propylene oxide))-(poly(ethylene oxide)) triblock copolymers, F68 or L64] + thiocyanate salts (ammonium, sodium, or potassium) + water at 25.0 °C. The influence of the nature of the cation on the formation of the ATPS was inves...
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Phase Diagrams, Densities, and Refractive Indexes of Aqueous Two-Phase Systems Comprising (F68, L64, or PEO1500) + (Ammonium, Sodium, or Potassium Thiocyanate Salts) + Water: Effect of Cation and Type of Macromolecule
2019Co-Authors: Maria C Hespanhol, Luis Henrique Mendes Da Silva, Beatriz M Fontoura, Vivianne Molica De Andrade, Aparecida Barbosa Mageste, Leandro Rodrigues De LemosAbstract:In extraction procedures, the more commonly used aqueous two-phase systems (ATPS) comprise mainly water, salt, and macromolecule, particularly the macromolecule poly(ethylene oxide) (PEO). However, one limitation of such ATPS is their capacity to separate compounds that are more hydrophobic. One possible solution to overcome this restriction is the use of ATPS formed with triblock copolymers, which are more hydrophobic and therefore enable the extraction of hydrophobic solutes. In addition, the range of applications of ATPS formed with thiocyanate salts can be broader, mainly to extract metal ions. In view of this, equilibrium data were acquired in this work by constructing phase diagrams for ATPS comprising Macromolecules [poly(ethylene oxide), PEO, or (poly(ethylene oxide))-(poly(propylene oxide))-(poly(ethylene oxide)) triblock copolymers, F68 or L64] + thiocyanate salts (ammonium, sodium, or potassium) + water at 25.0 °C. The influence of the nature of the cation on the formation of the ATPS was investigated and followed the order K+ > Na+ > NH4+. The capacity of different Macromolecules to enable ATPS formation was also examined and followed the order L64 > F68 > PEO1500. Phase inversion occurred with the (L64 or F68) + NH4SCN + water ATPS, in that the top phase is rich in salt and the bottom phase is rich in macromolecule. This aspect is different in most ATPS that are typically described in the literature
Frank Julicher - One of the best experts on this subject based on the ideXlab platform.
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liquid phase separation controlled by ph
Biophysical Journal, 2020Co-Authors: Omar Adamearana, Christoph Weber, Vasily Zaburdaev, Jacques Prost, Frank JulicherAbstract:Abstract We present a minimal model to study the effects of pH on liquid phase separation of Macromolecules. Our model describes a mixture composed of water and Macromolecules that exist in three different charge states and have a tendency to phase separate. This phase separation is affected by pH via a set of chemical reactions describing protonation and deprotonation of Macromolecules, as well as self-ionization of water. We consider the simple case in which interactions are captured by Flory-Huggins interaction parameters corresponding to Debye screening lengths shorter than a nanometer, which is relevant to proteins inside biological cells under physiological conditions. We identify the conjugate thermodynamic variables at chemical equilibrium and discuss the effective free energy at fixed pH. First, we study phase diagrams as a function of macromolecule concentration and temperature at the isoelectric point of the Macromolecules. We find a rich variety of phase diagram topologies, including multiple critical points, triple points, and first-order transition points. Second, we change the pH relative to the isoelectric point of the Macromolecules and study how phase diagrams depend on pH. We find that these phase diagrams as a function of pH strongly depend on whether oppositely charged Macromolecules or neutral Macromolecules have a stronger tendency to phase separate. One key finding is that we predict the existence of a reentrant behavior as a function of pH. In addition, our model predicts that the region of phase separation is typically broader at the isoelectric point. This model could account for both in vitro phase separation of proteins as a function of pH and protein phase separation in yeast cells for pH values close to the isoelectric point of many cytosolic proteins.
Athanasios I. Liapis - One of the best experts on this subject based on the ideXlab platform.
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molecular based modeling and simulation studies of water water and water macromolecule interactions in food and their effects on food dehydration
2013Co-Authors: Jee-ching Wang, Athanasios I. LiapisAbstract:A molecular dynamics (MD) modeling and simulation approach has been developed to study porous food systems constructed with amylose chains. The results indicate that food Macromolecules form porous structures and can make the adjacent water molecules strongly bound with reduced water activity and removal rate by providing additional water–macromolecule interactions that can significantly outweigh the reduction of the water–water interactions. These effects of pore structures are greater in systems with higher densities of food Macromolecules and smaller in size pores. During dehydration, water molecules can develop concave menisci in large pores and nonplanar interfaces between the dried and hydrated sections of the food, and thus water removal can be considered to start from the largest pores and, in particular, from the middle of the pores. Dehydration in general results in reduced pore sizes, a decreased number of pore openings, increased water–macromolecule interactions, and reduced overall thermal conductivity, so that more heat and longer times are needed to further dehydrate the porous materials. Additionally, the average minimum entropy requirement for food dehydration is greater in food systems with higher densities of food Macromolecules and lower water content.
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water water and water macromolecule interactions in food dehydration and the effects of the pore structures of food on the energetics of the interactions
Journal of Food Engineering, 2012Co-Authors: Jee-ching Wang, Athanasios I. LiapisAbstract:Abstract A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food Macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food Macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food Macromolecules, smaller in size pores, and stronger water–macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.
