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1.
Food Chem ; 305: 125441, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31494499

RESUMO

Samples of granular corn starch were treated with 1,4-α-glucan branching enzyme (GBE) for 20 h using three different methods. These GBE modification methods all increased glycosidic linkage ratio, cyclic glucan content, and proportion of short chains while reducing weight mean molecular weight. The in vitro digestion rates of the modified starches were suppressed. Among these methods, a novel two-stage modification method comprising a 10-h GBE treatment, gelatinization, and a second 10-h GBE treatment, produced samples with the lowest in vitro digestibility. The rapidly digestible starch content was 34.2% lower than that of the control and 18.0% lower than that of the product of one-stage modification with the same duration. Fine structure characterization showed that more cluster structures were proved during the two-stage modification. This two-stage method suppressed the digestibility of corn starch and increased the substrate concentration, showing great potential for the industrial processing of slowly-digestible starchy foods.

2.
Sensors (Basel) ; 19(20)2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31615076

RESUMO

This paper presents three-dimensional (3D) models of high-frequency piezoelectric micromachined ultrasonic transducers (PMUTs) based on the finite element method (FEM). These models are verified with fabricated aluminum nitride (AlN)-based PMUT arrays. The 3D numerical model consists of a sandwiched piezoelectric structure, a silicon passive layer, and a silicon substrate with a cavity. Two types of parameters are simulated with periodic boundary conditions: (1) the resonant frequencies and mode shapes of PMUT, and (2) the electrical impedance and acoustic field of PMUT loaded with air and water. The resonant frequencies and mode shapes of an electrically connected PMUT array are obtained with a laser Doppler vibrometer (LDV). The first resonant frequency difference between 3D FEM simulation and the measurement for a 16-MHz PMUT is reasonably within 6%, which is just one-third of that between the analytical method and the measurement. The electrical impedance of the PMUT array measured in air and water is consistent with the simulation results. The 3D model is suitable for predicting electrical and acoustic performance and, thus, optimizing the structure of high-frequency PMUTs. It also has good potential to analyze the transmission and reception performances of a PMUT array for future compact ultrasonic systems.

3.
Curr Mol Med ; 19(5): 364-375, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30914023

RESUMO

BACKGROUND: The homeostasis of palmitoylation and depalmitoylation is involved in various cellular processes, the disruption of which induces severe physiological consequences. Acyl-protein thioesterase (APT) and palmitoyl-protein thioesterases (PPT) catalyze the depalmitoylation process. The natural mutation in human PPT1 caused neurodegenerative disease, yet the understanding of APT1 remains to be elucidated. While the deletion of APT1 in mice turned out to be potentially embryonically lethal, the decoding of its function strictly relied on the identification of its substrates. OBJECTIVE: To determine the potential substrates of APT1 by using the generated human APT1 knockout cell line. METHODS: The combined techniques of palmitoyl-protein enrichment and massspectrometry were used to analyze the different proteins. Palmitoyl-proteins both in HEK293T and APT1-KO cells were extracted by resin-assisted capture (RAC) and data independent acquisition (DIA) quantitative method of proteomics for data collection. RESULTS: In total, 382 proteins were identified. The gene ontology classification segregated these proteins into diverse biological pathways e.g. endoplasmic reticulum process and ubiquitin-mediated proteolysis. A few potential substrates were selected for verification; indeed, major proteins were palmitoylated. Importantly, their levels of palmitoylation were clearly changed in APT1-KO cells. Interestingly, the proliferation of APT1-KO cells escalated dramatically as compared to that of the WT cells, which could be rescued by APT1 overexpression. CONCLUSION: Our study provides a large scale of potential substrates of APT1, thus facilitating the understanding of its intervened molecular functions.

4.
Int J Biol Macromol ; 107(Pt B): 1758-1764, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29030183

RESUMO

Granular corn starch, waxy corn starch, potato starch and tapioca starch were modified using the α-d-glucan branching enzyme (1,4-α-d-glucan:1,4-α-d-glucan 6-α-d-(1,4-α-d-glucano)-transferase, GBE, EC 2.4.1.18) from Geobacillus thermoglucosidans. The GBE-catalyzed modification caused a time-dependent increase in the ratios of α-1,6 linkages to total glycosidic linkages, as well as reductions in the average chain length and relative crystallinity. These modifications lowered the in vitro digestibility of the starch. Modification with GBE caused varying degrees of change in the in vitro digestibility of starches obtained from different sources. The highest slowly digestible starch (SDS) and resistant starch (RS) contents were found in modified tapioca starch. After modification of tapioca starch with GBE for 10h, the ratio of α-1,6 linkages to total glycosidic linkages was increased by 11.5%, while its relative crystallinity was decreased by 22.9%. Meanwhile, the SDS and RS contents of tapioca starch were increased by 47.3% and 13.5%, respectively. These results demonstrate that the digestibility of starch can be lowered through GBE modification, which may aid the development of modified starches that are digested more slowly.


Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana/metabolismo , Amido/metabolismo , Cristalização , Glicosídeos/química , Espectroscopia de Prótons por Ressonância Magnética , Difração de Raios X
5.
Biotechnol Adv ; 35(5): 619-632, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28457999

RESUMO

As member of glycosyl hydrolase family 13, maltooligosaccharide-forming amylases (MFAses) are specific and interesting because of their capacity to hydrolyze starch into functional maltooligosaccharides, which are usually composed of 2-10 α-d-glucopyranosyl units linked by α-1,4 glycosidic linkages. MFAses have been extensively studied during recent decades, and have shown promise in various industrial applications. This review begins by introducing the potential uses of maltooligosaccharides. Then it describes the progress in the identification, assay, action pattern, structure, and modification of MFAses. The review continues with tips concerning the preparation of MFAses, which aim to improve MFAse production to meet the needs of industry. Finally, the industrial uses of MFAses are described, focusing on the production of maltooligosaccharides and application in the bread industry. Recent progress has demonstrated that the MFAses are poised to become important industrial catalysts.


Assuntos
Amilases/química , Oligossacarídeos/química , Amido/química , Glicosídeos/química , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Especificidade por Substrato , Temperatura Ambiente
6.
Int J Biol Macromol ; 97: 679-687, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28122205

RESUMO

Waxy corn starch was modified with the 1,4-α-glucan branching enzyme (GBE) from Geobacillus thermoglucosidans STB02. Incubating waxy corn starch with GBE increased the number of α-1,6 branch points and reduced the average chain length. Enzymatic modification also decreased the breakdown and setback values of Brabender viscosity curves, indicating that the modified starch had higher paste stability. Preheating the starch at 65°C for 30min before incubation with GBE could promote enzymatic modification of starch. Linear regression was used to describe the relationships between starch structure and its pasting and thermal properties. The setback value showed a negative linear correlation with the α-1,6 branch point content (R2=0.9824) and a positive linear correlation with the average chain length (R2=0.8954). Meanwhile, the gelatinization enthalpy was also linearly correlated to the α-1,6 branch point content (R2=0.9326) and the average chain length (R2=0.8567). These insights provide a useful reference for food processors.


Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana/metabolismo , Amido/química , Temperatura Ambiente , Ceras/química , Zea mays/química , Geobacillus/enzimologia , Glicosídeos/química , Pomadas , Amido/metabolismo
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