Shapely polysaccharides. The eighth Colworth Medal Lecture

Rees, D. A.

doi:10.1042/bj1260257

Cited by 372 publications

(71 citation statements)

References 40 publications

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“…A similar effect has been proposed for explaining the higher stability constant found for polymers of galacturonic acid with respect to the monomer [18]. At very low total divalent cation concentration the association constant increases continuously.…”

Section: +(1)supporting

confidence: 67%

Stability constants for the complexation of alkali and alkaline‐earth cations byN‐acetyl‐neuraminic acid

Behr

Lehn

1972

FEBS Letters

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Section: +(1)supporting

confidence: 67%

Stability constants for the complexation of alkali and alkaline‐earth cations byN‐acetyl‐neuraminic acid

Behr

Lehn

1972

FEBS Letters

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“…Compared to κ-carrageenan or agarose gels at the same concentration, the mixed gels with LBG present increased gel strength and elasticity, and a reduced tendency toward syneresis. 2,5,6 Such synergic interactions observed with LBG were found to decrease in magnitude when other galactomannans with higher galactose contents were considered. 2 However, experimental data have shown that guar gum (GG), the galactomannan from Cyamopsis tetragonolobus seeds with a M/G of approximately 2:1, is effective in producing an increase in viscosity when blended with xanthan gum.…”

Section: Introductionmentioning

confidence: 95%

Characterisation of Prosopis juliflora seed gum and the effect of its addition to kappa-carrageenan systems

Azero¹,

Andrade²

2006

J. Braz. Chem. Soc.

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A galactomanana de Prosopis juliflora (PJ) foi obtida por extração em água, a 50 °C, a partir de sementes moídas. As suas características estruturais e as propriedades em solução foram comparadas com as de uma amostra comercial de goma guar (GG). Após degradação parcial, as amostras resultantes foram submetidas à espectroscopia de 13 C RMN. As razões manose/galactose de PJ (M/G = 1,64) e de GG (M/G = 1,85) foram determinadas a partir das áreas relativas aos picos atribuídos a C-1. A expansão das linhas do C-4 revelaram diferenças na estrutura fina das duas galactomananas. A viscosidade intrínseca determinada para a amostra de GG, [η] = 10,3 dL g -1 , foi ligeiramente maior do que a determinada para a PJ, [η] = 9,4 dL g -1 . Experimentos dinâmicos realizados nas mesmas concentrações mostraram comportamentos viscoelásticos similares para as duas gomas. Nenhum aumento no módulo de armazenamento (G′) foi observado para misturas κ-carragenana/PJ em 0,1 mol L -1 KCl em uma concentração total de 1,0 g L -1 , em relação à κ-carragenana sozinha. Géis fortes, obtidos pela mistura de κ-carragenana e PJ ou GG em 0,25 mol L -1 KCl em uma concentração total de 10 g L -1 apresentaram propriedades mecânicas similares.The galactomannan from Prosopis juliflora (PJ galactomannan) was extracted from milled seeds in water at 50 o C. Its structural and solution properties were characterised in comparison with a commercial sample of guar gum (GG galactomannan). After partial degradation, the resulting samples were submitted to 13 C-NMR spectroscopy. The mannose to galactose (M/G) ratios of PJ (M/G = 1.64) and GG (M/G = 1.85) galactomannans were estimated from the relative peak areas of the corresponding C-1 lines. Expansion of the C-4 lines revealed differences in the fine structure of the two galactomannans. The intrinsic viscosity determined for the GG sample, [η] = 10.3 dL g -1 , was slightly higher than that determined for PJ galactomannan, [η] = 9.4 dL g -1 . Dynamic experiments carried out at the same concentrations showed similar viscoelastic behaviours for the two gums. No enhancement in the storage modulus (G′) was observed for κ-carrageenan/PJ mixed solution in 0.1 mol L -1 KCl at 1.0 g L -1 total polymer concentration, in relation to κ-carrageenan alone. Self-supporting gels obtained by mixing κ-carrageenan and PJ or GG galactomannans in 0.25 mol L -1 KCl at 10 g L -1 total polymer concentration displayed similar mechanical properties.

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“…All SMS measurements were performed in buffer A (5 mM each MES, potassium phosphate, HEPES, sodium borate, and CAPS buffers, pH 6.0, 75 mM sodium chloride) unless otherwise specified. For microscopy samples that require confinement of the DsRed, agarose gels (100-200 nm estimated pore size 17 ) were employed to provide a largely aqueous matrix. 2.0% agarose (w/v, from Boehringer Mannheim) was melted, cooled slowly to 37°C in a water bath, mixed thoroughly with protein solution, and incubated for 15 min at 37°C.…”

Section: Methodsmentioning

confidence: 99%

Photophysics of DsRed, a Red Fluorescent Protein, from the Ensemble to the Single-Molecule Level

et al. 2001

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DsRed, a tetrameric fluorescent protein cloned from the Discosoma genus of coral, has shown promise as a longer-wavelength substitute for green fluorescent protein (GFP) mutants for in vivo protein labeling. Bulk and single-molecule studies of the recombinant protein revealed that the DsRed chromophore shows high stability against photobleaching as compared to GFP mutants. Stark modulation spectra confirm that the electronic structure of the DsRed chromophore is similar to that of GFP. However, the tetrameric nature of DsRed leads to intersubunit energy transfer, as evidenced by the molecule's unusually low fluorescence anisotropy when immobilized (0.23 ( 0.02). This value is approximately consistent with an estimate of the energy transfer rates based on preliminary crystallographic information. The fluorescence emission bleaches at a rate linear in the applied excitation intensity, implying that the cessation of emission during pumping at 532 nm is light-driven and, consistent with the tetrameric structure, several photobleaching "steps" were observed for individual complexes. Because more photons are emitted before bleaching, this study suggests that DsRed may be superior to some GFP-based labeling technologies as long as tetramerization is not an issue in physiological studies. IntroductionSingle-molecule spectroscopy (SMS) continues to play a unique role in the elucidation of the dynamics of an increasingly broad range of complex systems. 14,25 By removing the averaging inherent in ensemble measurements, SMS yields a measure of the distribution of molecular properties which is of importance in systems that display static or time-dependent heterogeneity. Concurrently, developments in fluorescence microscopy have made the observation of single molecules of biological interest possible under a wide range of experimental conditions. 26 This versatility can be exploited to examine the molecular complexity of many biological systems.One critical challenge to the application of SMS techniques to biomolecules, especially in vivo, is the introduction of a fluorophore that acts as a reporter of activity, local environment, or spatial location. While certain important proteins display useful amounts of visible fluorescence arising from native cofactors, 12 most require the attachment of an extrinsic fluorophore to serve as the probe. The genetic fusion of naturally fluorescent proteins to a protein of interest ensures a consistent 1:1 stoichiometry in the cell, without the need for external chemical reactions. While the green fluorescent protein (GFP) and its mutants have proved suitable for many applications, 22,27 the relatively high quantum yield of photobleaching (∼10× that for a rhodamine dye 16 ) leaves room for improvement in applications that require a large number of emitted photons, such as in single-molecule studies. Also, no mutant of GFP has been demonstrated to be a strong emitter at long (>550 nm) wavelengths, where the interference from endogenous fluorophores is substantially less severe.Considering th...

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Shapely polysaccharides. The eighth Colworth Medal Lecture

Cited by 372 publications

References 40 publications

Stability constants for the complexation of alkali and alkaline‐earth cations byN‐acetyl‐neuraminic acid

Stability constants for the complexation of alkali and alkaline‐earth cations byN‐acetyl‐neuraminic acid

Characterisation of Prosopis juliflora seed gum and the effect of its addition to kappa-carrageenan systems

Photophysics of DsRed, a Red Fluorescent Protein, from the Ensemble to the Single-Molecule Level

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