Molecular mobility and dynamic site heterogeneity in amorphous lactose and lactitol from erythrosin B phosphorescence

Shirke, S. D.; You, Yumin; Ludescher, Richard D.

doi:10.1016/j.bpc.2006.05.001

Cited by 14 publications

(15 citation statements)

References 73 publications

(131 reference statements)

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“…At ∆T=−55°C, the emission energy was 14,830 cm -1 in sucrose, 14,810; 14,650; 14,600; 14,470; 14,510; and 14,480 cm -1 in G2 to G7, respectively, and 14,510 cm -1 in MD 18 (Table 2). Since the phosphorescence emission peak frequency provides a measure of the average energy of emission, a decrease in emission energy for molecules of similar chemical structure and composition reflects an increase in the average extent of dipolar relaxation around the excited triplet state before emission 13,15,34 . The decrease in emission energy with molecular weight thus suggests an increase with molecular weight in the extent of dipolar relaxation in the matrix environment around the The total decrease in emission energy from 5 to 100°C provides a measure of the average extent of dipolar relaxation around the probe excited state in these amorphous matrixes (Table 2).…”

Section: Resultsmentioning

confidence: 99%

“…The applicability of such a dynamic picture to biomolecule glasses is supported by evidence of spectral heterogeneity in Ery B phosphorescence in amorphous dried sugars and sugar alcohols [13][14][15] and in dried proteins 27,46 , indicating that dynamic site heterogeneity may be a characteristic feature of amorphous solid foods and other biomaterials. The Ery B phosphorescence emission bandwidth (Γ), the intensity decay stretching exponent (β), and variations in k TS0 and β across the excitation and emission bands all provide information about dynamic site heterogeneity in these amorphous sugar matrixes.…”

Section: Effect Of Molecular Size On Molecular Mobility In Sugarmentioning

confidence: 89%

“…The principle is that phosphorescence spectroscopy of triplet probes can examine the slow mobility motions occurring on the milliseconds to seconds time scale in highly viscous glasses and melts. Ery B is a food grade phosphorescence probe which has been found to be very sensitive to the molecular mobility in amorphous sugars [13][14][15][16][17][18][19][20]22,25,26 and proteins 27,28 . By embedding Ery B within the amorphous matrix, we can collect signals from probe molecules that are surrounded by matrix molecules and respond to the slow modes of mobility in local environments.…”

Section: Glass Transition Temperatures Of Oligosaccharides Asmentioning

confidence: 99%

“…The dynamic effect of matrix composition varies depending on the properties of the matrix molecules, the concentration of additive, and the temperature [14][15][16][17][18][19][20] . Composite matrixes composed of sucrose and glycerol 16 , of maltose and maltitol 14 , or of lactose and lactitol 15 , for example, all show lower molecular mobility than the corresponding matrixes composed of the pure sugar, while a sucrose matrix containing added biopolymer, either gelatin 19 , xanthan 20 , amylose, or maltodextrin 21 , displayed higher molecular mobility under some concentration conditions than the pure sucrose matrix. Since all of the additives have higher T g than sucrose, such results cannot be explained by the simple hypothesis that composition modulates matrix molecular mobility solely by modulating matrix T g .…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Molecular Size on Molecular Mobility in Amorphous Oligosaccharides

You

Ludescher

2010

Food Biophysics

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The physical properties and especially the molecular mobility of amorphous carbohydrate matrixes directly influence the stability of foods, feeds, and pharmaceuticals and the dessication tolerance of animals and plants during anhydrobiosis. Phosphorescence of the sodium salt of erythrosin B was used to investigate the local molecular mobility in pure amorphous solids of a homologous series of malto-oligosaccharides (maltose, G 2 ; maltotriose, G 3 ; maltotetraose, G 4 ; maltopentaose, G 5 ; maltohexaose, G 6 ; and maltoheptaose, G 7 ); sucrose and maltodextrin DE18 (a hydrolytic fraction of starch) were investigated for comparison. Measurements of the temperature-dependence of the phosphorescence emission energy, an indicator of the extent of local dipolar relaxation, and the phosphorescence emission lifetime, an indicator of the rate of collisional quenching of the excited state by matrix molecules, demonstrate that the local matrix molecular mobility increases with molecular size, and thus, with an increase in T g , in these glucose oligosaccharides. Master curves of the spectroscopic measures of matrix mobility for each oligosaccharide, plotted against T-T g , were not superimposable, suggesting that local properties of the amorphous sugar matrixes, rather than T g per se, influence local matrix mobility. Indicators of spectral heterogeneity also varied with molecular size, indicating that dynamic site heterogeneity also increased with molecular size and thus, T g . These results emphasize the importance of additional research in developing appropriate "molecular rules" for designing amorphous matrix systems with better long-term stability for foods, feeds, or pharmaceuticals.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Molecular Size On Molecular Mobility In Sugarmentioning

confidence: 89%

Section: Glass Transition Temperatures Of Oligosaccharides Asmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Effect of Molecular Size on Molecular Mobility in Amorphous Oligosaccharides

You

Ludescher

2010

Food Biophysics

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“…This gradual upward curvature at higher temperature is suggestive of a broad dynamic transition within the protein matrix rather than a sharp glass transition; an abrupt increase in slope of the Arrhenius plot is seen in sucrose, 26 maltose 33 and lactose. 50 To better illustrate the similarities in curvature of the Arrhenius plots, the apparent activation energies for triplet state quenching were estimated at each temperature T using a linear fit to the three points at T±10°C; these values are plotted for each protein as a function of temperature in Figure 3. For α-La, β-Lg, BSA, and soy 11S, despite the differences in <k TS0 >, the apparent activation energies are similar across the entire temperature range studied; this suggests that the modes of motion responsible for deactivation of Ery B are similar in these four globular proteins.…”

Section: 32mentioning

confidence: 99%

Photophysical Probes of the Amorphous Solid State of Proteins

et al. 2010

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The properties of amorphous solid proteins influence the texture and stability of low-moisture foods, the shelf-life of pharmaceuticals, and the viability of seeds and spores. We have investigated the relationship between molecular mobility and oxygen permeability in dry food protein films-bovine α-lactalbumin (α-La), bovine β-lactoblobulin (β-Lg), bovine serum albumin (BSA), soy 11S globulin, and porcine gelatin-using phosphorescence from the triplet probe erythrosin B. Measurements of the phosphorescence decay in the absence (nitrogen) and presence (air) of oxygen versus temperature provide estimates of the non-radiative decay rate for matrixinduced quenching (k TS0 ) and oxygen quenching (k Q [O 2 ]) of the triplet state. Since the oxygen quenching constant is the product of the oxygen solubility ([O 2 ]) and a term (k Q ) proportional to the oxygen diffusion coefficient, it is a measure of the oxygen permeability through the films. For all proteins except gelatin, Arrhenius plots of k TS0 reveal a gradual increase of apparent activation energy across a broad temperature range starting at ∼50°C; this suggests that there is a steady increase in the available modes of molecular motion with increasing temperature within the protein matrix. Arrhenius plots for k Q [O 2 ] were linear for all proteins with activation energies ranging from 24 to 29 kJ/mol. The magnitude of the oxygen quenching constants varied in the different proteins; the rates were approximately 10-fold higher in α-La, β-Lg, and BSA than in 11S glycinin and gelatin. Although the rate of oxygen permeability was not directly affected by the increased mobility of the protein matrix, plots of k Q [O 2 ] versus k TS0 were linear over nearly three orders of magnitude in the protein films, suggesting that the matrix mobility plays a specific role in modulating oxygen permeability. This effect may reflect differences in matrix-free volume that directly influence both mobility and oxygen solubility.

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Vanillin Phosphorescence as a Probe of Molecular Mobility in Amorphous Sucrose

Tiwari

Ludescher

2009

J Fluoresc

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Changes in molecular mobility are important in defining the stability and quality of amorphous solid foods, pharmaceuticals, and other solid biomaterials. Predictions of stability must consider matrix mobility below and above T(g) (the glass transition temperature); measurement of molecular mobility in amorphous solids over time scales ranging from <10(-9) s to >10(8) s requires specialized methods. This research investigated how the steady-state and time-resolved emission and intensity of phosphorescence from vanillin (4-hydroxy-3-methoxy benzaldehyde), a common flavor compound, can be used to probe molecular mobility when dispersed within amorphous pure sucrose films. Phosphorescence emission spectra and time-resolved intensity decays, measured in sucrose as a function of temperature in the absence of oxygen, were strongly modulated by matrix molecular mobility. Temperature had a significant effect on vanillin phosphorescence peak frequency and bandwidth, intensity, and lifetime both in the glass and in the melt. Time-resolved phosphorescence intensity decays from vanillin were multiexponential both below and above the glass transition temperature, indicating that the pure (single component) amorphous matrix was dynamically heterogeneous on the molecular level. These data show that vanillin is a promising intrinsic probe of molecular mobility and dynamic heterogeneity in amorphous solid foods and perhaps pharmaceuticals.

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Molecular mobility and dynamic site heterogeneity in amorphous lactose and lactitol from erythrosin B phosphorescence

Cited by 14 publications

References 73 publications

The Effect of Molecular Size on Molecular Mobility in Amorphous Oligosaccharides

The Effect of Molecular Size on Molecular Mobility in Amorphous Oligosaccharides

Photophysical Probes of the Amorphous Solid State of Proteins

Vanillin Phosphorescence as a Probe of Molecular Mobility in Amorphous Sucrose

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