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Cold Spring Harbor Protocols Dec 2021Most analytical electrophoreses of proteins are achieved by separation in polyacrylamide gels under conditions that ensure dissociation of proteins into individual...
Most analytical electrophoreses of proteins are achieved by separation in polyacrylamide gels under conditions that ensure dissociation of proteins into individual polypeptide subunits and minimize aggregation. Most commonly, the anionic detergent sodium dodecyl sulfate (SDS) is used in combination with a reducing agent (β-mercaptoethanol or dithiothreitol) and with heating to dissociate proteins before loading onto the gel. SDS binding denatures the polypeptides and imparts a negative charge that masks their intrinsic charge. The amount of SDS bound is generally sequence-independent and proportional to molecular weight; at saturation, approximately one SDS molecule is bound per two amino acids, or ∼1.4 g of SDS per gram of polypeptide. Therefore, the migration of SDS-polypeptide complexes in an electric field is proportional to the relative size of the polypeptide chain, and its molecular weight can be estimated by comparison to protein markers of known molecular weight. However, hydrophobicity, highly charged sequences, and certain posttranslational modifications such as glycosylation or phosphorylation may also influence migration. Thus, the apparent molecular weight of modified proteins does not always accurately reflect the mass of the polypeptide chain. This protocol describes preparation and running of SDS-PAGE gels, followed by staining to detect proteins using Coomassie Brilliant Blue. Finally, the stained SDS-PAGE gel may be scanned to an image or preserved by drying.
Topics: Electrophoresis, Polyacrylamide Gel; Gels; Molecular Weight; Peptides; Proteins; Sodium Dodecyl Sulfate
PubMed: 34853120
DOI: 10.1101/pdb.prot102228 -
ACS Macro Letters Dec 2022Controlled radical polymerization techniques enable the synthesis of polymers with predetermined molecular weights, narrow molecular weight distributions, and controlled...
Controlled radical polymerization techniques enable the synthesis of polymers with predetermined molecular weights, narrow molecular weight distributions, and controlled architectures. Moreover, these polymerization approaches have been routinely shown to result in retained end-group functionality that can be reactivated to continue polymerization. However, reactivation of these end groups under conditions that instead promote depropagation is a viable route to initiate depolymerization and potentially enable closed-loop recycling from polymer to monomer. In this report, we investigate light as a trigger for thermal depolymerization of polymers prepared by reversible-addition-fragmentation chain-transfer (RAFT) polymerization. We study the role of irradiation wavelength by targeting the → π* and π → π* electronic transitions of the thiocarbonylthio end-groups of RAFT-generated polymers to enhance depolymerization via terminal bond homolysis. Specifically, we explore depolymerization of polymers with trithiocarbonate, dithiocarbamate, and -substituted dithiobenzoate end groups with the purpose of increasing depolymerization efficiency with light. As the wavelength decreases from the visible range to the UV range, the rate of depolymerization is dramatically increased. This method of photoassisted depolymerization allows up to 87% depolymerization efficiency within 1 h, results that may further the advancement of recyclable materials and life-cycle circularity.
Topics: Polymerization; Molecular Weight; Polymers
PubMed: 36469937
DOI: 10.1021/acsmacrolett.2c00603 -
Chemical Communications (Cambridge,... Jun 2023Reversible Addition-Fragmentation Chain Transfer (RAFT) step-growth polymerization is an emerging method that synergistically combines the benefits of RAFT... (Review)
Review
Reversible Addition-Fragmentation Chain Transfer (RAFT) step-growth polymerization is an emerging method that synergistically combines the benefits of RAFT polymerization (functional group and user-friendly nature) and step-growth polymerization (versatility of the polymer backbone). This new polymerization method is generally achieved by using bifunctional reagents of monomer and Chain Transfer Agent (CTA), that efficiently yield Single Monomer Unit Insertion (SUMI) adducts under stoichiometrically balanced conditions. This review covers a brief history of the RAFT-SUMI process and its transformation into RAFT step-growth polymerization, followed by a comprehensive discussion of various RAFT step-growth systems. Furthermore, characterizing the molecular weight evolution of step-growth polymerization is elaborated based on the Flory model. Finally, a formula is introduced to describe the efficiency of the RAFT-SUMI process, assuming rapid chain transfer equilibrium. Examples of reported RAFT step-growth and SUMI systems are then categorized based on the driving force.
Topics: Polymerization; Polymers; Molecular Weight
PubMed: 37287313
DOI: 10.1039/d3cc01087b -
Macromolecular Rapid Communications Mar 2021Green monomers, such as oxygen (O ), water (H O), and carbon dioxide (CO ), refer to a kind of natural reagents with abundant, nontoxic, cheap, environmentally friendly,... (Review)
Review
Green monomers, such as oxygen (O ), water (H O), and carbon dioxide (CO ), refer to a kind of natural reagents with abundant, nontoxic, cheap, environmentally friendly, renewable, and sustainable features. These monomers have been used in multicomponent polymerizations (MCPs) toward functional polymers. In this review, the recent development of MCPs involving green monomers of O -, H O-, and CO is summarized. The catalytic systems, polymerization conditions, the molecular weights, and potential applications of resultant polymers are briefly discussed. Furthermore, the existing challenges and the promising opportunities are concisely provided.
Topics: Catalysis; Macromolecular Substances; Molecular Weight; Polymerization; Polymers
PubMed: 33314433
DOI: 10.1002/marc.202000547 -
The Journal of Physical Chemistry. B Jul 2022Shear-thickening fluids that absorb the impact energy of high-velocity projectiles are of great interest for aerospace and body-armor applications. In such a frame, we...
Shear-thickening fluids that absorb the impact energy of high-velocity projectiles are of great interest for aerospace and body-armor applications. In such a frame, we investigate transient states of neat and aqueous polyelectrolytes (PE) having low molecular weights and containing poly([2-(methacryloyloxy)ethyl]trimethylammonium) as polycations and poly(acrylamide--acrylic acid) as polyanions. We compare results with those of bulk water. We employ nonequilibrium molecular dynamics to simulate oscillatory shear, mainly in the linear viscoelastic regime. We find that neat PE exhibits properties of a viscoelastic solid, whereas water and the aqueous mixture of PE conform to viscoelastic liquids with Maxwellian behavior at low angular frequencies. Terminal relaxation times are ∼0.499 and ∼1.385 ps for water and the aqueous mixture of PE, respectively. At high angular frequencies, storage moduli show anomalous behaviors that correspond to transitions between shear thinning and shear thickening in complex shear viscosities. The change in potential energy with the increase of the angular frequency is mainly driven by intramolecular interactions for neat PE, whereas short-range Coulomb interactions are the major contributions for water and the aqueous mixture of PE. Upon observation of the molecular configurations, only the local polyionic structure in the aqueous mixture of PE shows improvement when increasing the angular frequency, whereas the rest remains barely affected. Thus, the water structure in the aqueous mixture of PE allows the storage of energy elastically through the hydrogen-bond network at large angular frequencies, whereas the mechanical contribution of polyions weakens and fully vanishes at the beginning of shear thinning, explaining the superimposed data with data of bulk water. Our method and findings set the path for future molecular simulations in the nonlinear viscoelastic regime with more complex underlying molecular mechanisms.
Topics: Molecular Conformation; Molecular Weight; Polyelectrolytes; Viscosity; Water
PubMed: 35732066
DOI: 10.1021/acs.jpcb.2c01448 -
Frontiers in Immunology 2022
Topics: Humans; Immune Checkpoint Inhibitors; Immunotherapy; Molecular Weight; Neoplasms
PubMed: 35663988
DOI: 10.3389/fimmu.2022.920442 -
Carbohydrate Research Nov 2019Fucoidan is a unique polysaccharide that has various biological activities partly owing to its capability to act as mimetics of natural ligands of protein receptors.... (Review)
Review
Fucoidan is a unique polysaccharide that has various biological activities partly owing to its capability to act as mimetics of natural ligands of protein receptors. However, its use is limited due to a number of reasons including those associated with molecular weight and composition variation in relation to an algae type and habitat, raw material collection time, extraction method and duration. The main problem which limits its application in therapy is high molecular weight and seasonal composition. To expand the scope of its application, it is necessary to develop a validated procedure of high-molecular-weight fucoidan depolymerization or synthesis of its oligomeric elements . Therefore, there is a need for the synthesis of polysaccharideoligomeric components and/or polymer mimetics which allow for the creation of chains with a certain degree of sulfation, molecular weight and yield. This paper presents the most commonly used methods of fucoidan homopolysaccharide and heteropolysaccharide fragments synthesis as well as problems associated with their synthesis, including fucoidan analogues available in the form of glycopolymers that are obtained by using different methods of radical polymerization. These fucoidan mimetic glycopolymers have a biological activity similar to that of native fucoidans with high yield, which allows for their use as potential agents in the pharmaceutical industry.
Topics: Chemistry Techniques, Synthetic; Molecular Weight; Polymerization; Polysaccharides
PubMed: 31526929
DOI: 10.1016/j.carres.2019.107806 -
International Journal of Cosmetic... Aug 2021Cosmetic emulsions containing hyaluronic acid are ubiquitous in the cosmetic industry. However, the addition of (different molecular weight) hyaluronic acid can affect...
OBJECTIVE
Cosmetic emulsions containing hyaluronic acid are ubiquitous in the cosmetic industry. However, the addition of (different molecular weight) hyaluronic acid can affect the filament stretching properties of concentrated emulsions. This property is often related to the "stringiness" of an emulsion, which can affect the consumer's choice for a product. It is thus very important to investigate and predict the effect of hyaluronic acid on the filament stretching properties of cosmetic emulsions.
METHODS
Model emulsions and emulsions with low and high molecular weights are prepared and their filament stretching properties are studied by the use of an extensional rheometer. Two different stretching speeds are employed during the stretching of the emulsions, a low speed at 10 µm/s and a high speed at 10 mm/s. The shear rheology of the samples is measured by rotational rheology.
RESULTS
We find that filament formation only occurs at high stretching speeds when the emulsion contains high molecular weight hyaluronic acid. The formation of this filament, which happens at intermediate states of the break-up, coincides with an exponential decay in the break-up dynamics. The beginning and end of the break-up of high molecular weight hyaluronic acid emulsions show a power law behaviour, where the exponent depends on the initial stretching rate. At a lower stretching speed, no filament is observed for both high molecular weight and low molecular weight hyaluronic acid emulsions and the model emulsion. The emulsions show a power law behaviour over the whole break-up range, where the exponent also depends on the stretching rate. No significant difference is observed between the shear flow properties of the emulsions containing different molecular weights hyaluronic acid.
CONCLUSION
In this work, we underline the importance of the molecular weight of hyaluronic acid on the elongational properties of concentrated emulsions. The filament formation properties, for example the stringiness, of an emulsion is a key determinant of a product liking and repeat purchase. Here, we find that high molecular weight hyaluronic acid and a high stretching speed are the control parameters affecting the filament formation of an emulsion.
Topics: Cosmetics; Emulsions; Hyaluronic Acid; Molecular Weight; Rheology
PubMed: 34008867
DOI: 10.1111/ics.12711 -
Polimery W Medycynie 2021Fucoidans represent the sulfated heteropolysaccharides that possess a wide range of important pharmacological properties. The properties of a fucoidan depend on several... (Review)
Review
Fucoidans represent the sulfated heteropolysaccharides that possess a wide range of important pharmacological properties. The properties of a fucoidan depend on several factors, including the molecular weight and the way of extraction. However, the selection of an optimal depolymerization method is necessary to enhance its therapeutic applications. Reducing the molecular weight of fucoidans will make it possible to use them in creating nanoparticles and nanocarriers for, among others, the targeted drug delivery. The molecular mass of the polymer can be changed by means of various methods of depolymerization. In this work, the possibility of application of ultrasonic destruction for decrease in the size of fucoidan molecules for the purpose of expansion of opportunities and spheres of their therapeutic application is considered. This is one of the simple and effective methods of depolymerization of fucoidan, which leads to a decrease in molecular weight without significant structural changes in macromolecules. In addition, methods and potential applications of the ultrasonic extraction of fucoidan from seaweed and the possibilities of their combination are discussed, as well as other physical or chemical methods of extraction.
Topics: Molecular Weight; Nanoparticles; Polysaccharides; Ultrasonics
PubMed: 34910386
DOI: 10.17219/pim/143961 -
Molecular Diversity May 2021Respiratory sensitization has been considered an important toxicological endpoint, because of the severe risk to human health. A great part of sensitization events were...
Respiratory sensitization has been considered an important toxicological endpoint, because of the severe risk to human health. A great part of sensitization events were caused by low molecular weight (< 1000) respiratory sensitizers in the past decades. However, there is currently no widely accepted test method that can identify prospective low molecular weight respiratory sensitisers. Herein, we performed the study of modeling and insights into molecular basis of low molecular weight respiratory sensitizers with a high-quality data set containing 136 respiratory sensitizers and 518 nonsensitizers. We built a number of classification models by using OCHEM tools, and a consensus model was developed based on the ten best individual models. The consensus model showed good predictive ability with a balanced accuracy of 0.78 and 0.85 on fivefold cross-validation and external validation, respectively. The readers can predict the respiratory sensitization of organic compounds via https://ochem.eu/article/114857 . The effect of several molecular properties on respiratory sensitization was also evaluated. The results indicated that these properties differ significantly between respiratory sensitizers and nonsensitizers. Furthermore, 14 privileged substructures responsible for respiratory sensitization were identified. We hope the models and the findings could provide useful help for environmental risk assessment.
Topics: Allergens; Machine Learning; Models, Molecular; Molecular Weight; Respiratory Hypersensitivity
PubMed: 32166484
DOI: 10.1007/s11030-020-10069-3