bluuebunny/crossref_metadata_2025 huggingface dataset:
Head–Head and Head–Tail Interaction: A General Mechanism for Switching Off Myosin II Activity in Cells
Authors: Jung Hyun Suk , Komatsu Satoshi , Ikebe Mitsuo , Craig Roger
Published: May 2008

Intramolecular interaction between myosin heads, blocking key sites involved in actin-binding and ATPase activity, appears to be a critical mechanism for switching off vertebrate smooth-muscle myosin molecules, leading to relaxation. We have tested the hypothesis that this interaction is a general mechanism for switching off myosin II–based motile activity in both muscle and nonmuscle cells. Electron microscopic images of negatively stained myosin II molecules were analyzed by single particle image processing. Molecules from invertebrate striated muscles with phosphorylation-dependent regulation showed head–head interactions in the off-state similar to those in vertebrate smooth muscle. A similar structure was observed in nonmuscle myosin II (also phosphorylation-regulated). Surprisingly, myosins from vertebrate skeletal and cardiac muscle, which are not intrinsically regulated, undergo similar head–head interactions in relaxing conditions. In all of these myosins, we also observe conserved interactions between the ‘blocked’ myosin head and the myosin tail, which may contribute to the switched-off state. These results suggest that intramolecular head–head and head-tail interactions are a general mechanism both for inducing muscle relaxation and for switching off myosin II–based motile activity in nonmuscle cells. These interactions are broken when myosin is activated.
The Role of Myosin II in Glioma Invasion of the Brain
Authors: Beadle Christopher , Assanah Marcela C. , Monzo Pascale , Vallee Richard , Rosenfeld Steven S. , Canoll Peter
Published: May 2008

The ability of gliomas to invade the brain limits the efficacy of standard therapies. In this study, we have examined glioma migration in living brain tissue by using two novel in vivo model systems. Within the brain, glioma cells migrate like nontransformed, neural progenitor cells—extending a prominent leading cytoplasmic process followed by a burst of forward movement by the cell body that requires myosin II. In contrast, on a two-dimensional surface, glioma cells migrate more like fibroblasts, and they do not require myosin II to move. To explain this phenomenon, we studied glioma migration through a series of synthetic membranes with defined pore sizes. Our results demonstrate that the A and B isoforms of myosin II are specifically required when a glioma cell has to squeeze through pores smaller than its nuclear diameter. They support a model in which the neural progenitor-like mode of glioma invasion and the requirement for myosin II represent an adaptation needed to move within the brain, which has a submicrometer effective pore size. Furthermore, the absolute requirement for myosin II in brain invasion underscores the importance of this molecular motor as a potential target for new anti-invasive therapies to treat malignant brain tumors.
Aquaporin-4 Dynamics in Orthogonal Arrays in Live Cells Visualized by Quantum Dot Single Particle Tracking
Authors: Crane Jonathan M. , Van Hoek Alfred N. , Skach William R. , Verkman A. S.
Published: May 2008

Freeze-fracture electron microscopy (FFEM) indicates that aquaporin-4 (AQP4) water channels can assemble in cell plasma membranes in orthogonal arrays of particles (OAPs). We investigated the determinants and dynamics of AQP4 assembly in OAPs by tracking single AQP4 molecules labeled with quantum dots at an engineered external epitope. In several transfected cell types, including primary astrocyte cultures, the long N-terminal “M1” form of AQP4 diffused freely, with diffusion coefficient ∼5 × 10−10cm2/s, covering ∼5 μm in 5 min. The short N-terminal “M23” form of AQP4, which by FFEM was found to form OAPs, was relatively immobile, moving only ∼0.4 μm in 5 min. Actin modulation by latrunculin or jasplakinolide did not affect AQP4-M23 diffusion, but deletion of its C-terminal postsynaptic density 95/disc-large/zona occludens (PDZ) binding domain increased its range by approximately twofold over minutes. Biophysical analysis of short-range AQP4-M23 diffusion within OAPs indicated a spring-like potential, with a restoring force of ∼6.5 pN/μm. These and additional experiments indicated that 1) AQP4-M1 and AQP4-M23 isoforms do not coassociate in OAPs; 2) OAPs can be imaged directly by total internal reflection fluorescence microscopy; and 3) OAPs are relatively fixed, noninterconvertible assemblies that do not require cytoskeletal or PDZ-mediated interactions for formation. Our measurements are the first to visualize OAPs in live cells.
Comparative Study of Activity and Heat Stability of Limit Dextrinase in 16 Barley Cultivars
Authors: Li Fen , Zhang Jun‐e , Liu Hong‐Mei , Tian Shu‐juan , Yang Xian‐Guang , Ma Ji‐Xian , Sun Meng‐Xiang
Published: May 2008

We conducted a comprehensive study of 15 cultivars of Chinese barley and one cultivar of European barley to examine and compare the activity and heat stability of limit dextrinase (LD) among them. Our results revealed that the enzymatic activity of LD drops dramatically at incubation temperatures >65°C, indicating that 65°C is the point of incubation temperature sensitivity for this enzyme. Compared with the European barley cultivar Triumph, the levels of enzymatic activity and heat stability of LD in most Chinese barley cultivars included in this study were low, except for Jipi 2 and 92001, which were nearly equal to Triumph. We also found that the activity and heat stability of LD were strongly influenced by the genotype and growth environment of the cultivar, which suggests that genetic manipulation and optimal cultivation conditions may be useful in producing high‐quality barley for the brewing industry.
Extractability, Structure and Molecular Weight of β‐Glucan from Canadian Rye (Secale cereale L.) Whole Meal
Authors: Ragaee S. M. , Wood P. J. , Wang Q. , Tosh S. , Brummer Y.
Published: May 2008

Oat and barley (1→3)(1→4)‐β‐d‐glucans (β‐glucan) are readily extracted by hot water but rye β‐glucan is resistant to such extraction. This poor extractability might be due to entrapment within a matrix of arabinoxylan (AX) cross‐linked through phenolic constituents. AX are the major nonstarch polysaccharides of the rye kernel. In this study, several approaches were compared in an effort to determine optimum conditions for extraction of high yields, high molecular weight (MW), and high purity of β‐glucan from Canadian rye whole meal. Variables investigated included sodium hydroxide concentrations, extraction time, sample prehydration, extraction under low temperature, and prior extraction of AX with barium hydroxide. There was a linear relationship between the strength of NaOH and amount of β‐glucan extracted and because MW was essentially the same up to 1.0N NaOH, this extraction agent, at room temperature for 90 min, was selected to isolate rye β‐glucan. The β‐glucan was then purified and structure and molecular weight distribution studied.
Role of Gluten in Flour Tortilla Staling
Authors: Alviola J. N. , Waniska R. D. , Rooney L. W.
Published: May 2008

Effects of protease and transglutaminase (TG) on dough and tortilla microstructures, shelf‐stability, and protein profile were determined to infer the role of gluten in tortilla staling. Control and enzyme‐treated tortillas were prepared using a standard bake test procedure and evaluated for three weeks. Confocal micrographs of control dough showed thin protein strands forming a continuous web‐like matrix. Protease‐treated dough had pieces of proteins in place of the continuous matrix, while TG‐treated dough had thicker protein strands that were heterogeneously distributed. Control tortillas had a well‐distributed continuous protein structure. Protease‐treated tortilla had a continuous structure despite being composed of hydrolyzed proteins in the dough, while the TG‐treated tortilla retained clumps of proteins. Both treatments resulted in shorter shelf‐stability of tortillas. An evenly distributed and moderately stronger gluten network is necessary for longer retention of tortilla flexibility. Solubility of protein fractions differed among treatments, but molecular weight distribution did not differentiate control and treated dough or tortillas. The proportion of each protein fraction appears to affect staling.
Effects of Transglutaminase on Rheology, Microstructure, and Baking Properties of Frozen Dough
Authors: Huang W. N. , Yuan Y. L. , Kim Y. S. , Chung O. K.
Published: May 2008

The improving effects of transglutaminase (TGase) were investigated on the frozen dough system and its breadmaking quality. Rheological properties and microstructure of fresh and frozen doughs were measured using a Rapid Visco‐Analyser (RVA), dynamic rheometer, and scanning electron microscopy (SEM). The frozen doughs with three storage periods (1, 3, and 5 weeks at –18°C) were studied at three levels (0.5, 1.0, and 1.5%) of TGase. As the amount of TGase increased, hot pasting peak viscosity and final viscosity from the RVA decreased, but breakdown value increased. The TGase content showed a positive correlation with both storage modulus G′ (elastic modulus) and the loss modulus G″ (viscous modulus): G′ was higher than G″ at any given frequency. The SEM micrographs showed that TGase strengthened the gluten network of fresh, unfrozen dough. After five weeks of frozen storage at –18°C, the gluten structure in the control dough appeared less continuous, more disrupted, and separated from the starch granules, while the dough containing 0.5% TGase showed less fractured gluten network. Addition of TGase increased specific volume of bread significantly (P < 0.05) with softer bread texture. Even after the five weeks of frozen storage, bread volume from dough with 1.5% TGase was similar to that of the fresh control bread (P < 0.05). The improving effects of TGase on frozen dough were likely the result of the ability of TGase to polymerize proteins to stabilize the gluten structure embedded by starch granules in frozen doughs.
Effects of Sorghum Type and Milling Process on the Sensory Characteristics of Sorghum Porridge
Authors: Kebakile Martin M. , Rooney Lloyd W. , de Kock Henriette L. , Taylor John R. N.
Published: May 2008

Improvement in the technology of sorghum grain milling for food use requires an in‐depth understanding of how grain type and milling process affect the sensory characteristics of the food product. In Africa and parts of India, the product is generally porridge. Porridges prepared from meals produced by milling 12 sorghum types using hand‐pounding, roller milling, and abrasive decortication followed by hammer milling were subjected to descriptive sensory analysis and data were analyzed by principal component analysis. Milling process had more effect than sorghum type on porridge sensory characteristics. Porridges from roller‐milled sorghum were generally darker, had more specks, were more astringent, and had enhanced branny aroma. Porridges from hand‐pounded meals were more stiff and coarse but had rancid off‐flavor and humus odor. Porridges obtained with abrasive decortication and hammer milling were lighter in color, had enhanced cereal aroma, and were moderately more intense in most other attributes. Sorghums with pigmented pericarps and soft endosperms generally produced dark, specky, and astringent porridges with branny aroma, while light‐colored hard grains produced light‐colored porridges with enhanced cereal flavor and aroma. For high‐quality sorghum porridge, abrasive decortication and hammer milling were the best milling processes in addition to using light‐colored hard grain.
Effects of Steeping Temperatures and Periods of Waxy Rice on Expansion Properties of Gangjung (a traditional Korean oil‐puffed rice snack)
Authors: Kim Haeng Ran , Kim Kyung Mi , Lee Hye‐Seong , Kim Kwang Ok
Published: May 2008

This study was conducted to investigate the effect of steeping conditions of waxy rice, temperatures (15, 25, and 35°C) and time periods (1, 11, and 21 days) on the expansion ratio of gangjung (a traditional Korean oil‐puffed rice snack). Physicochemical properties of waxy rice flour steeped under various conditions and expansion properties of gangjung made of the steeped waxy rice flour were investigated, and multiple regression analyses were applied between those properties to identify major physicochemical factors that optimally predict the expansion ratio of gangjung. As steeping temperature and time periods of waxy rice changed from the lowest to the highest, the expansion ratio of gangjung markedly increased (from 1,022 to 2,533%). Yet, the expansion ratio of the waxy rice sample steeped for 11–21 days at 35°C was not significantly different from the sample steeped for 21 days at 25°C, indicating that the lengthy steeping process for gangjung making can be shortened by increasing the steeping temperature. Physicochemical properties include moisture (γ = 0.85), protein (γ = –0.91), ash (γ = –0.84), potassium (γ = –0.89), magnesium (γ = –0.88), phosphorous (γ = –0.91), peak viscosity (γ = 0.77), and breakdown (γ = 0.94) of steeped waxy rice flour. These properties were highly correlated with expansion ratio (P < 0.01). Multiple regression analysis showed that the expansion ratio of gangjung was predicted successfully by the phosphorous content and breakdown value of steeped waxy rice flour.
Relationship of Ethanol Yield to Agronomic and Seed Quality Characteristics of Small Grains
Authors: Lacerenza J. A. , Martin J. M. , Talbert L. E. , Lanning S. P. , Giroux M. J.
Published: May 2008

Production of fuel ethanol hinges on the availability of carbohydrate sources, with corn being the crop of choice in most areas. However, in some climatic regions, it is not feasible to grow adequate volumes of corn so other starch sources must be utilized. Here we examined various small grain crops commonly grown in the Northern Great Plains for suitability for ethanol production. Four cultivars each of the hexaploid wheat (Triticum aestivum L.) classes hard red spring (HRS), hard white spring (HWS), soft white spring (SWS), along with durum wheat (Triticum durum L.), and four spring barley (Hordeum vulgare L.) cultivars were grown in replicated plots in two environments in 2006. Agronomic and seed quality traits, along with starch content and ethanol yield over a period of 72 hr were measured on all cultivars. Agronomic yield was highest for the barley cultivars and lowest for HRS and HWS. Seed size was greatest for the durum and barley cultivars. The SWS group had the lowest protein content and the highest starch content. Starch content was highly correlated with final ethanol yield and the SWS group was highest in absolute ethanol yield. However, ethanol yield per hectare was highest for barley, with SWS ranking second, while the HRS and HWS groups had the lowest ethanol yields per hectare. The results indicate that selection for small grain ethanol yield should focus primarily upon agronomic yield at the expense of protein content. Traditional selection for high HRS and HWS milling and baking quality is not consistent with maximal ethanol yield per hectare.
Composite Durum Wheat Flour/Plantain Starch White Salted Noodles: Proximal Composition, Starch Digestibility, and Indigestible Fraction Content
Authors: Osorio‐Díaz Perla , Aguilar‐Sandoval Alondra , Agama‐Acevedo Edith , Rendón‐Villalobos Rodolfo , Tovar Juscelino , Bello‐Pérez Luis A.
Published: May 2008

In search of a way to improve the nutritional profile of noodles, we prepared them with various mixtures of durum wheat flour and isolated plantain starch, and tested their proximal composition. Cooked noodles were assessed for in vitro starch digestibility, indigestible fraction content, and predicted glycemic index. The protein content declined with the addition of plantain starch. Both total starch (TS) level and the content of starch available for digestible enzymes (AS) decreased as the plantain starch level increased, a pattern that may be related to increased starch lixiviation during cooking of noodles containing plantain starch. There was an inverse pattern for resistant starch (RS). RS content in control (durum wheat flour) noodles was ≈50% lower than in the samples containing plantain starch. The soluble indigestible fraction (SIF) content in all samples was higher than the insoluble counterpart (IIF). The total indigestible fraction varied according to the wheat substitution level. Although the hydrolysis index (HI) and predicted glycemic index (pGI) of plantain starch noodles were moderate and decreased as the plantain starch proportion rose. These composite noodles exhibited higher indices than the control sample, a phenomenon that may also be dependent on the product physical structure. Results indicate that in spite of the increased starch digestion rate, plantain starch noodles are a better source of indigestible carbohydrates than pure wheat starch pasta. This might have dietetic applications.
Effect of Moisture Content and Tempering Method on the Functional and Sensory Properties of Popped Sorghum
Authors: Gaul J. A. , Rayas‐Duarte P.
Published: May 2008

Red and white sorghum were tempered using two methods (direct and indirect) to adjust moisture content (MC) to 12, 14, and 17% and popped using a hot‐air popper. Kernel size, pericarp thickness, bulk density, popped kernel expansion volume and ratio, popped volume, and surface color were recorded. Forty‐six untrained panelists evaluated popped sorghum using a 9‐point hedonic scale and expressed preference using a paired comparison test. Sorghum with thicker pericarp (red) had higher percent popped, expansion ratio, and popped volume. In white sorghum, indirect tempering increased percent popped and tempering to 17% MC increased popped volume. Panelists significantly preferred popcorn in appearance (8.0 ± 1.0) and size (7.9 ± 1.0) to sorghum (6.6 ± 1.7 appearance and 5.6 ± 2.2 size for 12 and 17% MC tempering). Panelists equally preferred the taste of popcorn (7.1 ± 1.5) and popped sorghum tempered to 12% MC (6.4 ± 1.8) and 17% MC (6.9 ± 1.4). Sorghum pops were brighter, vividly whiter, and 5× smaller than popcorn.
Compressive Strength of Wheat Endosperm: Analysis of Endosperm Bricks
Authors: Morris Craig F. , Pitts Marvin J. , Bettge Arthur D. , Pecka Kameron , King Garrison E. , McCluskey Patrick J.
Published: May 2008

The material properties of wheat grain endosperm are central to its processing and end‐use quality. The preparation of geometrically‐defined endosperm specimens free of bran, germ, and pigment strand can facilitate the objective study of endosperm material properties. This study was conducted to characterize the material properties of wheat endosperm from two soft, two hard, and one durum wheat varietal samples. Additionally, each varietal sample was sorted according to vitreous or mealy kernel type. Endosperm ‘bricks’ approximately 0.76 × 2.08 × 1.06 mm were prepared using an abrading (Kernel Sanders, KS) device. Bricks were tested in compression using a texture analyzer (TA.XTPlus). Stress‐strain curves were used to calculate failure strain, failure stress, failure energy, and Young's modulus. Additionally, the effect of brick aging up to one month, and changes in moisture content (freeze drying, oven drying, and equilibration to ≈10.5–11% mc) were studied. Intrakernel variation was assessed by preparing two sibling bricks (one from each cheek) from individual kernels. Failure strain, stress, and energy all had relatively high model R2 values (0.68, 0.79, and 0.75, respectively). The ANOVA model R2 for Young's modulus was 0.46. All models indicated variety as a highly significant source of variation in brick material properties. The effect of vitreous versus mealy kernel type was not consistent across varietal samples. Brick age and moisture content did not significantly affect brick material properties. Analysis of sibling bricks indicated that the magnitude of intrakernel variation was similar to that observed for individual varietal lots of uniform vitreous or mealy kernel type. Overall, failure strain provided a ranking and mean separation most consistent with kernel texture market class. The results obtained in the present study, although similar to other published reports do not closely agree with them on the material properties of wheat endosperm. Similarly, published results of material properties often differ considerably. The source of these discrepancies are at present unknown, but in some circumstances they may relate to specimen orientation relative to the source kernel, as there was evidence for anisotropic behavior. A companion study compares the variation in kernel texture obtained with the single kernel characterization system (SKCS) with that obtained here using bricks.
Compressive Strength of Wheat Endosperm: Comparison of Endosperm Bricks to the Single Kernel Characterization System
Authors: Morris Craig F. , Bettge Arthur D. , Pitts Marvin J. , King G. E. , Pecka Kameron , McCluskey Patrick J.
Published: May 2008

The three major classes of endosperm texture (grain hardness) of soft and hard common, and durum wheat represent and define one of the leading determinants of the milling and end‐use quality of wheat. Although these three genetic classes are directly related to the Hardness locus and puroindoline gene function, much less is known about the kernel‐to‐kernel variation within pure varietal grain lots. Measurement of this variation is of considerable interest. The objective of this research was to compare kernel texture as determined by compression failure testing using endosperm bricks with results of whole‐kernel hardness obtained with the Single Kernel Characterization System 4100 hardness index (SKCS HI). In general terms, the variation obtained with the SKCS HI was of similar magnitude to that obtained using failure strain and failure energy of endosperm brick compression. Objective comparisons included frequency distribution plots, normalized frequency distribution plots, ANOVA model R2, and coefficients of variation. Results indicated that compression testing and SKCS HI similarly captured the main features of texture classes but also reflected notable differences in texture properties among and within soft, hard, and durum classes. Neither brick compression testing nor the SKCS HI may be reasonably expected to correctly classify all individual kernels as to genetic texture class. However, modest improvements in correct classification rate or, more importantly, better classification related to end‐use quality may still be achievable.
Endogenous Action of Cysteine Endopeptidase and Three Carboxypeptidases on Triticale Prolamins
Authors: Drzymała Adam , Prabucka Beata , Gajo Ilona , Bielawski Wiesław
Published: May 2008

Quantitative and qualitative changes occurring in the prolamin fraction in the starchy endosperm of triticale grains were analyzed by SDS‐PAGE on consecutive days of germination. The most intensive hydrolysis of prolamins was observed after the second day of the process. The high molecular weight fractions of prolamins were degraded with the highest rate. Endopeptidase EP8 was capable of hydrolyzing all fractions of prolamins isolated from dry triticale grains, but the high molecular weight fractions were the most rapidly degraded by the enzyme. Carboxypeptidases I, II, and III isolated from triticale grains hydrolyzed prolamins proteolytically modified by endopeptidase EP8, whereas intact prolamins were degraded slightly. Differences in the activity of the studied carboxypeptidases against crude prolamins indicate that carboxypeptidase II may be involved in the initiation of the hydrolysis process and, together with carboxypeptidases I and III, participates in the later stages of degradation of prolamins to amino acids. Experiments with exogenous GA3 demonstrated that the synthesis of EP8 is induced by this hormone and takes place in the aleurone layer. Mass spectrometry analysis showed the enzyme to be a homologue of barley endopeptidase EP‐A. Both enzymes belong to the cysteine class endopeptidases.
Effect of Storage Temperature and Flour Water Content on Lipids, Lipoxygenase Activity, and Oxygen Uptake During Dough Mixing
Authors: Maraschin Christelle , Robert Hughes , Boussard Aline , Potus Jacques , Baret Jean‐Luc , Nicolas Jacques
Published: May 2008

Flours differing in water content of 10% (F10), 12% (F12), and 14% (F14) were stored for 16 weeks at 22, 32, and 45°C. The major changes in lipids concerned the free fatty acids (increase) and the triglycerides (decrease). In all cases, the changes increased with increasing storage temperature and water content. After 16 weeks of storage, the losses in lipoxygenase (LOX) activity increased with increasing flour moisture and storage temperature from 10% for F10 at 22°C to 100% for F14 at 45°C. At the end of storage at 22 and 32°C, the bread volumes decreased by 10 and 25%, respectively, with no statistical differences (P < 0.05) between the samples. At 45°C, the volume losses were equal to 35, 46, and 61% for the F10, F12, and F14 samples, respectively. In the same time, the flour oxidative ability (oxygen uptake during dough mixing) increased for the F10 and F12 samples with increasing storage temperature, whereas it decreased for the F14 samples stored at 45°C. Therefore, provided the residual LOX activity is sufficient (omission of the F14 samples stored at 45°C), the flour oxidative ability increased during storage and is positively correlated to its oxidable PUFA content.
Influences of Acid and Alkali on Mechanical Properties of Compression‐Molded Gluten Bioplastics
Authors: Zhang Qibin , Song Yihu , Zheng Qiang
Published: May 2008

The present work was focused on the effects of acid and alkali on the uniaxial extensional deformation of gluten bioplastics compression‐molded at 80 and 110°C. Water absorption and morphology observation were also performed to characterize the properties and morphology of the gluten bioplastics. The results show that HCl did not show catalysis function for cross‐linking proteins at 80°C and even hindered the cross‐linking reaction at 110°C. On the other hand, NaOH generally accelerated the cross‐linking reaction during compression‐molding, thus significantly improving Young's modulus, tensile strength, and strain at break. However, an NaOH content >0.5 wt% could cause adverse effects at molding temperatures as high as 110°C.
Changes in Rice with Variable Temperature Parboiling: Thermal and Spectroscopic Assessment
Authors: Himmelsbach D. S. , Manful J. T. , Coker R. D.
Published: May 2008

Rapid visco analysis (RVA) and differential scannning calorimetry (DSC) provided overall assessments of the effects of variable temperature soaking at 30, 50, 70, and 90°C and steaming at 4, 8, and 12 min. Calculation of the relative parboiling index (RPI) and percent gelatinization provided good metrics for determining the overall effects of partial parboiling. FT‐Raman and solid‐state 13C CP‐MAS NMR spectroscopies provided insight to conformational changes in protein and starch of paddy rice under various parboiling conditions. RVA showed lower pasting curves and DSC showed lower ΔH with increased temperature and steaming times. A large decrease in viscosity occurred with only the 30‐4 treatment as opposed to raw rice. This observation was consistent with FT‐Raman results that indicated substantial conversion of the protein from α‐helix to other conformations. DSC indicated incomplete gelatinization of starch, even with 90°C soaking and 12 min of steaming. Solid‐state 13C CP‐MAS NMR spectroscopy confirmed this result. However, it indicated the percent of Vh/amorphous plus the remaining crystalline starch in the 90‐12 treatment was equal to the amorphous and partially‐ordered starch in commercially parboiled rice. These results suggest that partial parboiling, 90°C soaking, and more than 8 min of steaming (ideally ≈12 min) of paddy rice is sufficient to induce changes that inactivate enzymes and provide enough starch gelatinization to prevent kernel breakage.
Determining the Role of Starch in Flour Tortilla Staling Using α‐Amylase
Authors: Alviola J. Novie , Waniska Ralph D.
Published: May 2008

Effects of α‐amylase modification on dough and tortilla properties were determined to establish the role of starch in tortilla staling and elucidate the antistaling mechanism of this enzyme. Control and amylase‐treated tortillas were prepared using a standard bake test procedure, stored at 22°C, and evaluated over four weeks. Amylase improved shelf‐stability of tortillas. The enzyme also produced a significant amount of dextrins and sugars, decreased loss of amylose solubility, and weakened starch granules. Amylopectin crystallinity increased with time, but was similar for the control and treated tortillas. Staling of tortillas appears to mainly involve the starch in the amorphous phase. As such, amylase activity does not significantly interfere with amylopectin crystallization. It is proposed that amylase partially hydrolyzed the dispersed starch (i.e., mostly amylose), starch bridging the crystalline region, and protruding amylopectin branches. Starch hydrolysis decreases the rigid structure and plasticized polymers during storage. The flexibility of tortillas results from the combined functionalities of the amylose gel and amylopectin solidifying the starch granules during storage. Protein functionality may also be involved in tortilla staling, but this needs further research.
Influence of Cooking Conditions on the Protein Matrix of Sorghum and Maize Endosperm Flours
Authors: Ezeogu Lewis I. , Duodu K. Gyebi , Emmambux M. Naushad , Taylor John R. N.
Published: May 2008

To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three‐dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2‐mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β‐sheet structure relative to α‐helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disulfide bonding and an increase in β‐sheet structure occurred with cooking, with the increase in disulfide bonding being greatest in sorghum vitreous endosperm. The tendency for the sorghum protein matrix to collapse and mat more with cooking than the maize matrix appears to be due to greater disulfide bonding. This is responsible for the observed low starch digestibility of cooked sorghum flour as a result of the more disulfide‐bonded protein matrix limiting the expansion of the starch granules and hence amylase access.
Influence of Shaping and Orientation of Structures on Rheological Properties of Wheat Flour Dough Measured in Dynamic Shear and in Biaxial Extension
Authors: Davidou S. , Michon C. , Thabet I. Ben , Launay B.
Published: May 2008

Characterization of the rheological properties of wheat flour dough during mixing and baking without modifying its structure or mechanical properties is not easy. In this work, the effect of dough setting pre‐orientation and strain orientation during characterization are assessed for differently structured wheat flour doughs (various water contents and addition of glucose oxydase). Rheological properties were measured in dynamic shear as rotational (CSL2100 fitted with a cone‐plate geometry) or radial (CP20 fitted with a plate‐plate geometry) small deformation mode and in lubricated squeezing flow and relaxation called large deformation mode. In comparison with radial shearing, rotational shearing induces a much larger preorientation of the network and thus a strain‐hardening phenomenon that affects the rheological measurements (storage modulus is overestimated) but relaxes, at least partially, during a rest period. Consequently, a longer period of time has to be allotted (allowing stress relaxation) before starting measurements. Plate‐plate geometry induces less preorientation and allows measurement a few minutes after setting. However, it has less discrimination of the differently structured dough than the cone‐plate geometry used in rotational mode. Results which partially agree with those of the CP20 are obtained using the lubricated squeezing flow followed by stress relaxation.
Analysis of Quality Protein Changes in Nixtamalized QPM Flours as a Function of the Steeping Time
Authors: Rojas‐Molina I. , Gutiérrez E. , Cortés‐Acevedo M. E. , Falcón A. , Bressani R. , Rojas A. , Ibarra C. , Pons‐Hernández J. L. , Guzmán‐Maldonado S. H. , Cornejo‐Villegas A. , Rodríguez M. E.
Published: May 2008

This study showed the protein changes in Quality Protein Maize (QPM H‐368C) during the traditional nixtamalization process as a function of the steeping time from 0 to 15 hr. Protein content (N × 6.25), pH, protein fractionation, reactive lysine, essential amino acids, and protein digestibility were analyzed to explain the protein quality modifications in nixtamalized corn flours (NQF). The thermoalkaline process increased significantly (P ≤ 0.05) the protein content (5.57 ± 0.86%) in NQF obtained at 3, 5, 7, 9, 11, 13, and 15 hr of steeping time compared with native corn or corn without treatment (NC). The pH values of NQF were not proportional to the steeping time and significantly different (P ≤ 0.05) between them. At 5 hr critical steeping time, the total lysine and reactive lysine content decreased severely (36 and 32%, respectively) with statistical differences (P ≤ 0.05) compared with NC. On the other hand, the tryptophan content decreased significantly (P ≤ 0.05) at steeping times of 5–15 hr (38.70 ± 6.7%) compared with NC. The changes in the lysine and tryptophan content were not proportional to the steeping time. The protein recovery in the albumin and globulin fraction diminished (P ≤ 0.05) with respect to raw corn. The protein recovery for γ‐zeins, glutelin‐like proteins, glutelins, and residue increased. A significant (P ≤ 0.05) decrease was found in the essential amino acids in NQF with 3–7 hr of steeping time compared with NC. Equally important was the reduction in protein digestibility observed in NQF steeped at long steeping times (11–15 hr) with significant (P ≤ 0.05) differences compared with NC. The protein solubility distribution along the steeping step and the essential amino acids location, specifically lysine in corn kernel, could explain partially the protein quality changes observed in this research. Finally, these results contribute to reconciling discrepancies associated with the protein quality modifications in nixtamalized corn reported previously in literature.
Effects of Particle Size and Starch Damage of Flour and Alkaline Reagent on Yellow Alkaline Noodle Characteristics
Authors: Hatcher D. W. , Edwards N. M. , Dexter J. E.
Published: May 2008

A hard white spring wheat was milled to yield three patent flours with different starch damage levels by manipulating reduction grinding conditions, and each flour was sieved to give three different particle sizes (85–110, 110–132, 132–183 μm). Raw alkaline noodles were prepared using either 1% w/w kansui (sodium and potassium carbonates in 9:1 ratio) or 1% w/w sodium hydroxide. Noodles prepared with sodium hydroxide were significantly brighter, less red, and more yellow than those made with kansui. Differences in noodle color among flour treatments were evident but were attributable to differences in flour refinement rather to than particle size or starch damage. Noodles were rested for 1 hr after processing before cooking. Alkaline reagent was the main factor associated with cooking loss, being ≈50% greater for sodium hydroxide noodles because of higher pH compared with kansui noodles. Cooked sodium hydroxide noodles were thicker than kansui noodles, and cooked strands for both noodle types became thicker as starch damage increased and as particle size became coarser. Instrumental assessment of cooked noodle texture showed that maximum cutting stress (MCS), resistance to compression (RTC), recovery (REC), stress relaxation time (SRT), chewiness (CHE), and springiness (SPR) were influenced by the type of alkaline reagent. Flour particle size and starch damage also influenced noodle texture but the magnitude of the effects and the trends were dependent on alkaline reagent. MCS of kansui noodles was much greater than for sodium hydroxide noodles. MCS of kansui noodles increased as starch damage increased but, in contrast, MCS of sodium hydroxide noodles decreased with increasing starch damage. REC of kansui noodles increased with increasing starch damage and decreased with larger particle size, whereas for sodium hydroxide noodles REC decreased with increasing starch damage and declined dramatically with larger particle size. Kansui noodles exhibited significantly shorter SRT than sodium hydroxide noodles. SRT of kansui noodles was only moderately affected by starch damage and particle size, whereas for sodium hydroxide noodles, SRT became much shorter as flour became coarser and starch damage became higher. CHE of kansui noodles was greater than for sodium hydroxide noodles. CHE of kansui noodles increased as starch damage increased. In contrast, CHE of sodium hydroxide noodles decreased as starch damage increased and also decreased as flour became coarser. SPR of both noodle types decreased as flour became coarser and starch damage became greater. On the basis of these experiments, flour of smaller particle size is an asset to the cooking quality of sodium hydroxide noodles, but high starch damage is to be avoided. For kansui noodles, the impact of flour particle size on cooked noodle texture was less evident and low starch damage, rather than high starch damage, was an asset.
Barrier and Mechanical Properties of Starch‐Clay Nanocomposite Films
Authors: Tang Xiaozhi , Alavi Sajid , Herald Thomas J.
Published: May 2008

The poor barrier and mechanical properties of biopolymer‐based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch‐clay nanocomposites were synthesized by a melt extrusion method. Natural (MMT) and organically modified (I30E) montmorillonite clays were chosen for the nanocomposite preparation. The structures of the hybrids were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Films were made through casting using granulate produced by a twin‐screw extruder. Starch/MMT composite films showed higher tensile strength and better water vapor barrier properties than films from starch/I30E composites, as well as pristine starch, due to formation of intercalated nanostructure. To find the best combinations of raw materials, the effects of clay content (0–21 wt% MMT), starch sources (corn, wheat, and potato), and amylose content (≈0, 28, 55, 70, 100%) on barrier and mechanical properties of the nanocomposite films were investigated. With increase in clay content, significantly higher (15–92%) tensile strength (TS), and lower (22–67%) water vapor permeability (WVP) were obtained. The barrier and mechanical properties of nanocomposite films did not vary significantly with different starch sources. Nanocomposite films from regular corn starch had better barrier and mechanical properties than either high amylopectin or high‐amylose‐based nanocomposite films. WVP, TS, and elongation at break (%E) of the films did not change significantly as amylose content increased beyond 50%.
The enzyme aromatic amine dehydrogenase induces a substrate conformation crucial for promoting vibration that significantly reduces the effective potential energy barrier to proton transfer
Authors: Johannissen Linus O , Scrutton Nigel S , Sutcliffe Michael J
Published: May 2008

The role of promoting vibrations in enzymic reactions involving hydrogen tunnelling is contentious. While models incorporating such promoting vibrations have successfully reproduced and explained experimental observations, it has also been argued that such vibrations are not part of the catalytic effect. In this study, we have employed combined quantum mechanical/molecular mechanical methods with molecular dynamics and potential energy surface calculations to investigate how enzyme and substrate motion affects the energy barrier to proton transfer for the rate-limiting H-transfer step in aromatic amine dehydrogenase (AADH) with tryptamine as substrate. In particular, the conformation of the iminoquinone adduct induced by AADH was found to be essential for a promoting vibration identified previously—this lowers significantly the ‘effective’ potential energy barrier, that is the barrier which remains to be surmounted following collective, thermally equilibrated motion attaining a quantum degenerate state of reactants and products. When the substrate adopts a conformation similar to that in the free iminoquinone, this barrier was found to increase markedly. This is consistent with AADH facilitating the H-transfer event by holding the substrate in a conformation that induces a promoting vibration.
Balancing Newton's mind: his singular behaviour and his madness of 1692–93
Authors: Keynes Milo
Published: May 2008

Newton grew up with a vulnerable and eccentric character besides having a low self-esteem, and he was someone who only uncommonly developed any close relationships. On review it is argued that his distrust and suspicions of others, and the fear that he might be harmed by criticism and his discoveries stolen, followed from his mother's separation from him in childhood and not, as has been claimed, from the developmental disorder of Asperger's syndrome. It is further firmly argued that his ‘madness’ of 1692 and 1693 was due to mercury poisoning from his alchemical experiments and not to clinical depression.
‘Magic coins’ and ‘magic squares’: the discovery of astrological sigils in the Oldenburg Letters
Authors: Roos Anna Marie
Published: May 2008

Enclosed in a 1673 letter to Henry Oldenburg were two drawings of a series of astrological sigils, coins and amulets from the collection of Strasbourg mathematician Julius Reichelt (1637–1719). As portrayals of particular medieval and early modern sigils are relatively rare, this paper will analyse the role of these medals in medieval and early modern medicine, the logic behind their perceived efficacy, and their significance in early modern astrological and cabalistic practice. I shall also demonstrate their change in status in the late seventeenth century from potent magical healing amulets tied to the mysteries of the heavens to objects kept in a cabinet for curiosos. The evolving perception of the purpose of sigils mirrored changing early modern beliefs in the occult influences of the heavens upon the body and the natural world, as well as the growing interests among virtuosi in collecting, numismatics and antiquities.
Cubature on Wiener space in infinite dimension
Authors: Bayer Christian , Teichmann Josef
Published: May 2008

We prove a stochastic Taylor expansion for stochastic partial differential equations (SPDEs) and apply this result to obtain cubature methods, i.e. high-order weak approximation schemes for SPDEs, in the spirit of Lyons and Victoir (Lyons & Victoir 2004Proc. R. Soc. A460, 169–198). We can prove a high-order weak convergence for well-defined classes of test functions if the process starts at sufficiently regular initial values. We can also derive analogous results in the presence of Lévy processes of finite type; here the results seem to be new, even in finite dimension. Several numerical examples are added.
Sexual selection in a lekking bird: the relative opportunity for selection by female choice and male competition
Authors: DuVal Emily H , Kempenaers Bart
Published: May 2008

Leks are classic models for studies of sexual selection due to extreme variance in male reproductive success, but the relative influence of intrasexual competition and female mate choice in creating this skew is debatable. In the lekking lance-tailed manakin (
Chiroxiphia lanceolata
), these selective episodes are temporally separated into intrasexual competition for alpha status and female mate choice among alpha males that rarely interact. Variance in reproductive success between status classes of adult males (alpha versus non-alpha) can therefore be attributed to male–male competition whereas that within status largely reflects female mate choice. This provides an excellent opportunity for quantifying the relative contribution of each of these mechanisms of sexual selection to the overall opportunity for sexual selection on males (
I
males
). To calculate variance in actual reproductive success, we assigned genetic paternity to 92.3% of 447 chicks sampled in seven years. Reproduction by non-alphas was rare and apparently reflected status misclassifications or opportunistic copulations en route to attaining alpha status rather than alternative mating strategies. On average 31% (range 7–44%,
n
=6 years) of the total
I
males
was due to variance in reproductive success between alphas and non-alphas. Similarly, in a cohort of same-aged males followed for six years, 44–58% of the total
I
males
was attributed to variance between males of different status. Thus, both intrasexual competition for status and female mate choice among lekking alpha males contribute substantially to the potential for sexual selection in this species.
Phylogenomic analyses of lophophorates (brachiopods, phoronids and bryozoans) confirm the Lophotrochozoa concept
Authors: Helmkampf Martin , Bruchhaus Iris , Hausdorf Bernhard
Published: May 2008

Based on embryological and morphological evidence, Lophophorata was long considered to be the sister or paraphyletic stem group of Deuterostomia. By contrast, molecular data have consistently indicated that the three lophophorate lineages, Ectoprocta, Brachiopoda and Phoronida, are more closely related to trochozoans (annelids, molluscs and related groups) than to deuterostomes. For this reason, the lophophorate groups and Trochozoa were united to Lophotrochozoa. However, the relationships of the lophophorate lineages within Lophotrochozoa are still largely unresolved. Maximum-likelihood and Bayesian analyses were performed based on a dataset comprising 11 445 amino acid positions derived from 79 ribosomal proteins of 39 metazoan taxa including new sequences obtained from a brachiopod and a phoronid. These analyses show that the three lophophorate lineages are affiliated with trochozoan rather than deuterostome phyla. All hypotheses claiming that they are more closely related to Deuterostomia than to Protostomia can be rejected by topology testing. Monophyly of lophophorates was not recovered but that of Bryozoa including Ectoprocta and Entoprocta and monophyly of Brachiozoa including Brachiopoda and Phoronida were strongly supported. Alternative hypotheses that are refuted include (i) Brachiozoa as the sister group of Mollusca, (ii) ectoprocts as sister to all other Lophotrochozoa including Platyzoa, and (iii) ectoprocts as sister or to all other protostomes except chaetognaths.