SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Molecular mass

27

The purpose of this study was to develop novel dissolving microneedle arrays fabricated from hyaluronic acid (HA) as a material and to improve the transdermal permeability of relatively high molecular weight drugs. In this study, fluorescein isothiocyanate-labeled dextran with an average molecular weight of 4 kDa (FD4) was used as a model drug with a relatively high molecular weight. The microneedle arrays significantly increased transepidermal water loss (TEWL) and reduced transcutaneous electrical resistance (TER), indicating that they could puncture the skin and create drug permeation pathways successfully. Both TEWL and TER almost recovered to baseline levels in the microneedle array group, and relatively small pathways created by the microneedles rapidly recovered as compared with those created by a tape stripping treatment. These findings confirmed that the microneedle arrays were quite safe. Furthermore, we found that the transdermal permeability of FD4 using the microneedle arrays was much higher than that of the FD4 solution. Furthermore, we found that the microneedle arrays were much more effective for increasing the amount of FD4 accumulated in the skin. These findings indicated that using novel microneedle arrays fabricated from HA is a very useful and effective strategy to improve the transdermal delivery of drugs, especially relatively high molecular weight drugs without seriously damaging the skin.

Concepts: Pharmacology, Molecule, Drug, Mass, Array, Atomic mass unit, Molecular mass

27

To study the preparation and separation of Konjac oligosaccharides, Konjac Glucomannan was degraded by the combination of γ-irradiation and β-mannanase, and then the degradation product was separated by ultrafiltration. To our interest, for most of Konjac oligosaccharides obtained by this method, the molecular mass was lower than 2200Da. In addition, the 1000Da molecular weight cut off membrane could effectively separate the Konjac oligosaccharides. In conclusion, the combination of γ-irradiation and β-mannanase was an efficient method to obtain Konjac oligosaccharides, and the oligosaccharides of molecular mass lower than 1000Da could be effectively separated by ultrafiltration.

Concepts: Molecule, Mass, Atomic mass unit, Molecular mass, Separation, Glucomannan, Konjac, Shirataki noodles

27

Lignin valorization practices have attracted a great deal of interest in recent years due to the large excess of lignin produced by the pulp and paper industry, together with second-generation bioethanol plants. In this work, a new lignin valorization approach is proposed. It involves ultrafiltration as a fractionation process to separate different molecular weight lignin fractions followed by a hydrogen-free, mild, hydrogenolytic, heterogeneously catalyzed methodology assisted by microwave irradiation to obtain simple phenolic, monomeric products by depolymerization using a nickel-based catalyst. The main products obtained were desaspidinol, syringaldehyde, and syringol; this proves the efficiency of the depolymerization conditions applied. The concentration of these observed compounds increased when the molecular weights of the lignin fractions increased. The applied depolymerization conditions, which take advantage of the use of formic acid as a hydrogen-donating solvent, did not generate any biochar in the systems.

Concepts: Oxygen, Acetic acid, Solvent, Vanillin, Molecular mass, Methanol, Formic acid, Pulp and paper industry

24

We previously reported that nanoparticles (NPs) coated with 10 kDa PEG were mucoadhesive. Here, we demonstrate that by increasing the surface density, PEG with molecular weight (MW) as high as 40 kDa can be used as a mucoinert NP surface coating.

Concepts: Molecule, Mass, In vivo, Coating, Atomic mass unit, Molecular mass, Charge density

23

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Concepts: Glucose, Vaccine, Mass, Polymer, Polysaccharide, Aspect ratio, Haemophilus influenzae, Molecular mass

8

Biodegradable polyesters with various tacticities have been synthesized by means of stereoselective ring-opening polymerization of racemic lactide and β-lactones but with limited side-chain groups. However, stereoselective synthesis of functional polyesters remains challenging from O-carboxyanhydrides that have abundant pendant side-chain functional groups. Herein we report a powerful strategy to synthesize stereoblock polyesters by stereoselective ring-opening polymerization of racemic O-carboxyanhydrides with the use of photoredox Ni/Ir catalysts and a selected Zn complex with an achiral ligand. The obtained stereoblock copolymers are highly isotactic with high molecular weights ( > 70 kDa) and narrow molecular weight distributions (Mw/Mn < 1.1), and they display distinct melting temperatures that are similar to their stereocomplex counterparts. Furthermore, in one-pot photoredox copolymerization of two different O-carboxyanhydrides, the use of such Zn complex mediates kinetic resolution of the comonomers during enchainment and shows a chirality preference that allows for the synthesis of gradient copolymers.

Concepts: Amine, Chemical reaction, Molecule, Stereochemistry, Polymer, Chemical synthesis, Synthesis, Molecular mass

5

Several key tuberculosis drugs including pyrazinamide, with a molecular weight of 123.1 g/mol, are smaller than the usual drug like molecules. Current drug discovery efforts focus on the screening of larger compounds with molecular weights centered around 400-500 g/mol. Fragment (molecular weight < 300 g/mol) libraries have not been systematically explored for antitubercular activity. Here we screened a collection of 1000 fragments, present in the Maybridge Ro3 library, for whole cell activity against Mycobacterium tuberculosis Twenty-nine primary hits showed dose-dependent growth inhibition equal or better than pyrazinamide. The most potent hit, indole propionic acid (IPA, 3-(1H-indol-3-yl)propanoic acid), a metabolite produced by the gut microbiota, was profiled in vivo The molecule was well tolerated in mice and showed adequate pharmacokinetic properties. In an acute mouse model of tuberculosis infection, IPA reduced the bacterial load in the spleen 7 fold. Our results suggest that IPA should be evaluated as an add-on to current regimens and that fragment libraries should be further explored to identify antimycobacterial lead candidates.

Concepts: Oxygen, Pharmacology, Bacteria, Gut flora, Molecule, Tuberculosis, Butyric acid, Molecular mass

3

This study investigated the potential of bacterial-mediated polyethylene (PE) degradation in a two-phase microcosm experiment. During phase I, naturally weathered PE films were incubated for 6 months with the indigenous marine community alone as well as bioaugmented with strains able to grow in minimal medium with linear low-density polyethylene (LLDPE) as the sole carbon source. At the end of phase I the developed biofilm was harvested and re-inoculated with naturally weathered PE films. Bacteria from both treatments were able to establish an active population on the PE surfaces as the biofilm community developed in a time dependent way. Moreover, a convergence in the composition of these communities was observed towards an efficient PE degrading microbial network, comprising of indigenous species. In acclimated communities, genera affiliated with synthetic (PE) and natural (cellulose) polymer degraders as well as hydrocarbon degrading bacteria were enriched. The acclimated consortia (indigenous and bioaugmented) reduced more efficiently the weight of PE films in comparison to non-acclimated bacteria. The SEM images revealed a dense and compact biofilm layer and signs of bio-erosion on the surface of the films. Rheological results suggest that the polymers after microbial treatment had wider molecular mass distribution and a marginally smaller average molar mass suggesting biodegradation as opposed to abiotic degradation. Modifications on the surface chemistry were observed throughout phase II while the FTIR profiles of microbially treated films at month 6 were similar to the profiles of virgin PE. Taking into account the results, we can suggest that the tailored indigenous marine community represents an efficient consortium for degrading weathered PE plastics.

Concepts: Archaea, Bacteria, Mass, Polymer, Polyethylene, Plastics, Molecular mass, Linear low-density polyethylene

3

To date, dozens of stress-induced cellular senescence phenotypes have been reported. These cellular senescence states may differ substantially from each other, as well as from replicative senescence through the presence of specific senescence features. Here, we attempted to catalog virtually all of the cellular senescence-like states that can be induced by low molecular weight compounds. We summarized biological markers, molecular pathways involved in senescence establishment, and specific traits of cellular senescence states induced by more than fifty small molecule compounds.

Concepts: Molecule, Radical, Gerontology, Chemical compound, Molecular mass, Biological immortality, Leonard Hayflick

3

The suite of currently used drugs can be divided into two categories - traditional ‘small molecule’ drugs with typical molecular weights of <500 Da but with oral bioavailability, and much larger 'biologics' typically >5000 Da that are not orally bioavailable and need to be delivered via injection. Due to their small size, conventional small molecule drugs may suffer from reduced target selectivity that often ultimately manifests in human side-effects, whereas protein therapeutics tend to be exquisitely specific for their targets due to many more interactions with them, but this comes at a cost of low bioavailability, poor membrane permeability, and metabolic instability. The time has now come to reinvestigate new drug leads that fit between these two molecular weight extremes, with the goal of combining advantages of small molecules (cost, conformational restriction, membrane permeability, metabolic stability, oral bioavailability) with those of proteins (natural components, target specificity, high potency). This article uses selected examples of peptides to highlight the importance of peptide drugs, some potential new opportunities for their exploitation, and some difficult challenges ahead in this field.

Concepts: Protein, Pharmacology, Molecule, Atom, Drugs, Biochemistry, Molecular mass, Small molecule