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Carbohydrate Polymers Jul 2012In this study, an Aureobasidium pullulans SZU 1001 mutant, deficient in pigment production, was screened by complex UV and γ-ray mutagenesis. Medium composition...
In this study, an Aureobasidium pullulans SZU 1001 mutant, deficient in pigment production, was screened by complex UV and γ-ray mutagenesis. Medium composition optimization for increased pullulan molecular weight and production was conducted using this mutant. Six nutrients: yeast extract, (NH4)2SO4, K2HPO4, NaCl, MgSO4·7H2O and CaCl2 were detected within pullulan production in flasks. It is shown that NaCl and K2HPO4 have significant influences on molecular weight of pullulan, while yeast extract and (NH4)2SO4 significantly affect pullulan yield. To achieve a higher molecular weight and more efficient pullulan production, a response surface methodology approach was introduced to predict an optimal nutrient combination. A molecular weight of 5.74 × 10(6) and pullulan yield on glucose of 51.30% were obtained under batch pullulan fermentation with the optimized media, which increased molecular weight and pullulan production by 97.25% and 11.04%, respectively compared with the control media.
Topics: Glucans; Molecular Weight; Pigments, Biological
PubMed: 24750882
DOI: 10.1016/j.carbpol.2012.04.038 -
Environmental Science & Technology Aug 2017Brown carbon (BrC) consists of those organic compounds in atmospheric aerosols that absorb solar radiation and may play an important role in planetary radiative forcing...
Brown carbon (BrC) consists of those organic compounds in atmospheric aerosols that absorb solar radiation and may play an important role in planetary radiative forcing and climate. However, little is known about the production and loss mechanisms of BrC in the atmosphere. Here, we study how the light absorptivity of BrC from wood smoke and secondary BrC generated from the reaction of ammonium sulfate with methylglyoxal changes under photolytic aging by UVA radiation in the aqueous phase. Owing to its chemical complexity, BrC is separated by molecular weight using size exclusion chromatography, and the response of each molecular weight fraction to aging is studied. Photolytic aging induced significant changes in the light absorptivity of BrC for all molecular weight fractions; secondary BrC was rapidly photoblenched, whereas for wood smoke BrC, both photoenhancement and photobleaching were observed. Initially, large biomass burning BrC molecules were rapidly photoenhanced, followed by slow photolysis. As a result, large BrC molecules dominated the total light absorption of aged biomass burning BrC. These experimental results further support earlier observations that large molecular weight BrC compounds from biomass burning can be relatively long-lived components in atmospheric aerosols, thus more likely to have larger impacts on aerosol radiative forcing and could serve as biomass burning tracers.
Topics: Aerosols; Atmosphere; Biomass; Carbon; Molecular Weight
PubMed: 28640603
DOI: 10.1021/acs.est.7b01739 -
Biopolymers Jan 1967
Topics: Chemical Phenomena; Chemistry; Gelatin; Molecular Weight
PubMed: 6035929
DOI: 10.1002/bip.1967.360050106 -
Biotechnology Progress 2000High affinity, low molecular weight anionic displacers were successfully employed for the purification of antisense oligonucleotides. Several important structural...
High affinity, low molecular weight anionic displacers were successfully employed for the purification of antisense oligonucleotides. Several important structural characteristics were identified that contribute to the affinity of low molecular weight displacers to a hydrophilized polystyrene divinyl benzene anion exchanger. Sulfonic acid groups were found to possess higher affinity than carboxylic acid and phosphate functionalities, and nonspecific interactions (particularly hydrophobic interactions) were shown to play a major role in the retention process on this stationary phase material. Using this information, two high affinity, low molecular weight displacers were identified. These molecules are relatively inexpensive organic dyes that possess multiple sulfonic acid moieties, as well as aromatic functionalities, which increase nonspecific interactions with the stationary phase. These high affinity displacers, which can be readily detected, were then employed to displace several strongly retained antisense oligonucleotides that could not be displaced by previously established low molecular weight displacers. The displacement process resulted in very high purities of the antisense oligonucleotides. The results presented in this paper are significant in that they demonstrate that low molecular weight displacers for ion-exchange chromatography can possess equal to or greater affinities than their higher molecular weight counterparts, when nonspecific interactions with the stationary phase are exploited. In addition, the results illustrate the high resolutions possible with displacement chromatography and demonstrate an attractive technology for the process scale purification of oligonucleotides.
Topics: Chromatography, High Pressure Liquid; Molecular Weight; Oligonucleotides
PubMed: 11101335
DOI: 10.1021/bp0000860 -
Macromolecular Rapid Communications Aug 2015Nanoscale polymer thin films exhibit strong confinement effects on Tg arising from free surfaces. However, the coupled influence of molecular weight (MW) and surface...
Nanoscale polymer thin films exhibit strong confinement effects on Tg arising from free surfaces. However, the coupled influence of molecular weight (MW) and surface effects on Tg is not well understood for low MW film systems below the entanglement length. Utilizing atomistically informed coarse-grained molecular dynamics simulations for poly(methyl methacrylate) (PMMA), it is demonstrated that the decrease in free-standing film Tg with respect to bulk is more significant for low MW compared to high MW systems. Investigation of the local interfacial properties reveals that the increase in the local free volume near the free surface is greater for low MW, explaining the MW dependence of Tg -confinement behaviors. These findings corroborate recent experiments on low MW films, and highlight the relationship between nanoconfinement phenomena and local free volume effects arising from free surfaces.
Topics: Glass; Molecular Weight; Polymers
PubMed: 26033661
DOI: 10.1002/marc.201500194 -
Macromolecular Rapid Communications Mar 2024Conjugated polymers exhibit excellent electrical and mechanical properties when their molecular weight (M) is above the critical molecular weight (M). The...
Conjugated polymers exhibit excellent electrical and mechanical properties when their molecular weight (M) is above the critical molecular weight (M). The microstructural changes of polymers under strain are crucial to establish a structure-performance relationship. Herein, the tensile deformation of P(NDI2OD-T2) is visualized, and cracks are revealed either along the (100) crystal plane of side chain packing or along the main chain direction which depends on the M is below or above the M. When M < M, the film cracks along the (100) plane under small strains. When M > M, the polymer chains first undergo stretch-induced orientation and then fracture along the main chain direction at large strains. This is attributed to the fact that the low M film exhibits large crystalline domains and the absence of interdomain connectivity, which are vulnerable to mechanical stress. In contrast, the high M film displays a nearly amorphous morphology with adequate entanglements, the molecular chains can endure stresses in the stretching direction to release substantial strain energy under greater mechanical deformation. Therefore, the film with M > M exhibits the optimal electrical and mechanical performances simultaneously, i.e., the electron mobility is retained under 100% strain and after 100 stretching-releasing cycles.
Topics: Molecular Weight; Polymers; Stress, Mechanical
PubMed: 38018318
DOI: 10.1002/marc.202300624 -
Nature May 1949
Topics: Molecular Weight; Nucleic Acids
PubMed: 18144280
DOI: 10.1038/163849a0 -
Biophysical Chemistry Jan 1978The viscoelastic properties of T2 DNA solutions are used to determine the NaDNA molecular weight in four independent ways from the theory of the beads-springs model. The...
The viscoelastic properties of T2 DNA solutions are used to determine the NaDNA molecular weight in four independent ways from the theory of the beads-springs model. The four molecular weights are 131.9, 132.7, 130.5, and 127.6 X 10(6). The average of these values, adjusted for the probable errors in viscoelasticity and concentration measurements, is (126 +/- 5) X 10(6). The four molecular weights are termed Mtaugamma11, Mtaueta, Mtaugamma, and MtauA; each is different in its sensitivity to molecular weight distribution. Their agreement suggests (1) that the theoretical equations relating each M to the corresponding measured properties are valid, (2) that T2 DNA behaves as a partially free-draining polymer chain, and (3) that our solutions were nearly homogeneous in DNA size. We show that serious errors can result if the viscoelastic properties are not extrapolated to their limits at zero shear rate, as well as at zero DNA concentration, before calculating molecular weight.
Topics: Coliphages; DNA, Viral; Elasticity; Models, Theoretical; Molecular Weight; Viscosity
PubMed: 623866
DOI: 10.1016/0301-4622(78)85001-7 -
Journal of Dental Research Feb 1989The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained...
The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained by treatment of glass-ionomer cements as thermoplastic composites. Many of the concepts of polymer science can be applied successfully in a qualitative way to these cements, including the ideas of entanglements and reptation. Molecular weight of the polyacid had a pronounced influence on setting rate, acid erosion rate, toughness, fracture toughness, and wear resistance. The chain length of the polyacid was found to be an important parameter in formulation of a cement, and the higher the molecular weight, the better the properties. However, in practice the molecular weight is limited by viscosity, and some balance has to be achieved among concentration, molecular weight, and viscosity.
Topics: Acrylates; Chemical Phenomena; Chemistry, Physical; Dental Cements; Glass Ionomer Cements; Molecular Weight; Surface Properties; Viscosity
PubMed: 2918140
DOI: 10.1177/00220345890680021401 -
Biochimica Et Biophysica Acta Feb 1963
Topics: Lysine; Molecular Weight; Poly A
PubMed: 14002492
DOI: 10.1016/0006-3002(63)91272-1