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1.
J Neurosci ; 2024 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-38658168

RESUMO

Hexanucleotide repeat expansions within the gene C9ORF72 are the most common cause of the neurodegenerative diseases Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal dementia (FTD). This disease-causing expansion leads to a reduction in C9ORF72 expression levels in patients, suggesting loss of C9ORF72 function could contribute to disease. To further understand the consequences of C9ORF72 deficiency in vivo, we generated a c9orf72 mutant zebrafish line. Analysis of the adult female spinal cords revealed no appreciable neurodegenerative pathology such as loss of motor neurons, or increased levels of neuroinflammation. However, detailed examination of adult female c9orf72-/- retinas showed prominent neurodegenerative features, including a decrease in retinal thickness, gliosis, and an overall reduction in neurons of all subtypes. Analysis of rod and cone cells within the photoreceptor layer showed a disturbance in their outer segment structure and rhodopsin mis-localisation from rod outer segments to their cell bodies and synaptic terminals. Thus, C9ORF72 may play a previously unappreciated role in retinal homeostasis and suggests C9ORF72 deficiency can induce tissue specific neuronal loss.Significance statement Hexanucleotide expansions in the gene C9ORF72 are the most common cause of the Amyotrophic lateral sclerosis (ALS)/ Frontotemporal dementia (FTD) disease spectrum. The expansion reduces expression of C9ORF72 and so may play a role in neuronal loss. However, C9ORF72 loss of function has been comparatively understudied in vivo. Using the zebrafish as a model of C9ORF72 deficiency, we demonstrate that loss of C9ORF72 results in marked inflammation and neuronal loss in the aged adult zebrafish retina. Development of the retina is unaffected regardless of C9ORF72 status. This demonstrates that C9ORF72 loss of function can cause spontaneous neurodegeneration in vivo and highlights a novel role of C9ORF72 in retinal homeostasis.

2.
Methods Mol Biol ; 2778: 201-220, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38478280

RESUMO

Mitochondrial ß-barrel proteins fulfill crucial roles in the biogenesis and function of the cell organelle. They mediate the import and membrane insertion of proteins and transport of small metabolites and ions. All ß-barrel proteins are made as precursors on cytosolic ribosomes and are imported into mitochondria. The ß-barrel proteins fold and assemble with partner proteins in the outer membrane. The in vitro import of radiolabelled proteins into isolated mitochondria is a powerful tool to investigate the import of ß-barrel proteins, the folding of the ß-barrel proteins, and their assembly into protein complexes. Altogether, the in vitro import assay is a versatile and crucial assay to analyze the mechanisms of the biogenesis of mitochondrial ß-barrel proteins.


Assuntos
Proteínas Mitocondriais , Proteínas de Saccharomyces cerevisiae , Proteínas Mitocondriais/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Mitocôndrias/metabolismo , Transporte Proteico , Proteínas de Transporte da Membrana Mitocondrial/metabolismo
3.
Int J Biol Macromol ; 261(Pt 2): 129942, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38311131

RESUMO

Arabinoxylans, ß-glucans, and dextrins influence the brewing industry's filtration process and product quality. Despite their relevance, only a maximum concentration of ß-glucans is recommended. Nevertheless, filtration problems are still present, indicating that although the chemical concentration is essential, other parameters should be investigated. Molar mass and conformation are important polymer physical characteristics often neglected in this industry. Therefore, this research proposes an approach to physically characterize enzymatically isolated beer polysaccharides by asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index detector. Based on the obtained molar masses, root-mean-square radius (rrms from MALS), and hydrodynamic radius (rhyd), conformational properties such as apparent density (ρapp) and rrms/rhyd can be calculated based on their molar mass and size. Consequently, the ρapp and rrms/rhyd behavior hints at the different structures within each polysaccharide. The rrms/rhyd 1.2 and high ρapp values on low molar mass dextrins (1-2·105 g/mol) indicate branches, while aggregated structures at high molar masses on arabinoxylans and ß-glucans (2·105 -6·106 g/mol) are due to an increase of ρapp and a rrms/rhyd (0.6-1). This methodology provides a new perspective to analyze starch and non-starch polysaccharides in cereal-based beverages since different physical characteristics could influence beer's filtration and sensory characteristics.


Assuntos
Fracionamento por Campo e Fluxo , beta-Glucanas , Grão Comestível , Dextrinas , Polissacarídeos , Amido/química , Fracionamento por Campo e Fluxo/métodos , Espalhamento de Radiação
4.
Cell Rep ; 43(3): 113805, 2024 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-38377000

RESUMO

The majority of mitochondrial precursor proteins are imported through the Tom40 ß-barrel channel of the translocase of the outer membrane (TOM). The sorting and assembly machinery (SAM) is essential for ß-barrel membrane protein insertion into the outer membrane and thus required for the assembly of the TOM complex. Here, we demonstrate that the α-helical outer membrane protein Mco6 co-assembles with the mitochondrial distribution and morphology protein Mdm10 as part of the SAM machinery. MCO6 and MDM10 display a negative genetic interaction, and a mco6-mdm10 yeast double mutant displays reduced levels of the TOM complex. Cells lacking Mco6 affect the levels of Mdm10 and show assembly defects of the TOM complex. Thus, this work uncovers a role of the SAMMco6 complex for the biogenesis of the mitochondrial outer membrane.


Assuntos
Proteínas de Membrana Transportadoras , Proteínas de Saccharomyces cerevisiae , Proteínas de Membrana Transportadoras/metabolismo , Proteínas do Complexo de Importação de Proteína Precursora Mitocondrial , Proteínas de Transporte da Membrana Mitocondrial/genética , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Proteínas de Transporte/metabolismo , Transporte Proteico
5.
Cell Rep ; 43(3): 113772, 2024 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-38393949

RESUMO

The mitochondrial inner membrane plays central roles in bioenergetics and metabolism and contains several established membrane protein complexes. Here, we report the identification of a mega-complex of the inner membrane, termed mitochondrial multifunctional assembly (MIMAS). Its large size of 3 MDa explains why MIMAS has escaped detection in the analysis of mitochondria so far. MIMAS combines proteins of diverse functions from respiratory chain assembly to metabolite transport, dehydrogenases, and lipid biosynthesis but not the large established supercomplexes of the respiratory chain, ATP synthase, or prohibitin scaffold. MIMAS integrity depends on the non-bilayer phospholipid phosphatidylethanolamine, in contrast to respiratory supercomplexes whose stability depends on cardiolipin. Our findings suggest that MIMAS forms a protein-lipid mega-assembly in the mitochondrial inner membrane that integrates respiratory biogenesis and metabolic processes in a multifunctional platform.


Assuntos
Mitocôndrias , Membranas Mitocondriais , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Fosfolipídeos/metabolismo , Transporte de Elétrons , Cardiolipinas/metabolismo
6.
Cell Mol Gastroenterol Hepatol ; 17(6): 1025-1038, 2024 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-38325549

RESUMO

BACKGROUND & AIMS: This review was developed to provide a thorough and effective update on models relevant to esophageal metaplasia, dysplasia, and carcinogenesis, focusing on the advantages and limitations of different models of Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). METHODS: This expert review was written on the basis of a thorough review of the literature combined with expert interpretation of the state of the field. We emphasized advances over the years 2012-2023 and provided detailed information related to the characterization of established human esophageal cell lines. RESULTS: New insights have been gained into the pathogenesis of BE and EAC using patient-derived samples and single-cell approaches. Relevant animal models include genetic as well as surgical mouse models and emphasize the development of lesions at the squamocolumnar junction in the mouse stomach. Rat models are generated using surgical approaches that directly connect the small intestine and esophagus. Large animal models have the advantage of including features in human esophagus such as esophageal submucosal glands. Alternatively, cell culture approaches remain important in the field and allow for personalized approaches, and scientific rigor can be ensured by authentication of cell lines. CONCLUSIONS: Research in BE and EAC remains highly relevant given the morbidity and mortality associated with cancers of the tubular esophagus and gastroesophageal junction. Careful selection of models and inclusion of human samples whenever possible will ensure relevance to human health and disease.

7.
Nature ; 627(8003): 445-452, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38383785

RESUMO

Reversible modification of target proteins by ubiquitin and ubiquitin-like proteins (UBLs) is widely used by eukaryotic cells to control protein fate and cell behaviour1. UFM1 is a UBL that predominantly modifies a single lysine residue on a single ribosomal protein, uL24 (also called RPL26), on ribosomes at the cytoplasmic surface of the endoplasmic reticulum (ER)2,3. UFM1 conjugation (UFMylation) facilitates the rescue of 60S ribosomal subunits (60S) that are released after ribosome-associated quality-control-mediated splitting of ribosomes that stall during co-translational translocation of secretory proteins into the ER3,4. Neither the molecular mechanism by which the UFMylation machinery achieves such precise target selection nor how this ribosomal modification promotes 60S rescue is known. Here we show that ribosome UFMylation in vivo occurs on free 60S and we present sequential cryo-electron microscopy snapshots of the heterotrimeric UFM1 E3 ligase (E3(UFM1)) engaging its substrate uL24. E3(UFM1) binds the L1 stalk, empty transfer RNA-binding sites and the peptidyl transferase centre through carboxy-terminal domains of UFL1, which results in uL24 modification more than 150 Å away. After catalysing UFM1 transfer, E3(UFM1) remains stably bound to its product, UFMylated 60S, forming a C-shaped clamp that extends all the way around the 60S from the transfer RNA-binding sites to the polypeptide tunnel exit. Our structural and biochemical analyses suggest a role for E3(UFM1) in post-termination release and recycling of the large ribosomal subunit from the ER membrane.


Assuntos
Retículo Endoplasmático , Processamento de Proteína Pós-Traducional , Subunidades Ribossômicas Maiores de Eucariotos , Ubiquitina-Proteína Ligases , Sítios de Ligação , Biocatálise , Microscopia Crioeletrônica , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Membranas Intracelulares/química , Membranas Intracelulares/metabolismo , Membranas Intracelulares/ultraestrutura , Peptidil Transferases/química , Peptidil Transferases/metabolismo , Peptidil Transferases/ultraestrutura , Ligação Proteica , Proteínas Ribossômicas/química , Proteínas Ribossômicas/metabolismo , Proteínas Ribossômicas/ultraestrutura , Subunidades Ribossômicas Maiores de Eucariotos/química , Subunidades Ribossômicas Maiores de Eucariotos/metabolismo , Subunidades Ribossômicas Maiores de Eucariotos/ultraestrutura , RNA de Transferência/metabolismo , Especificidade por Substrato , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/ultraestrutura
8.
Dtsch Med Wochenschr ; 149(6): 290-297, 2024 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-38412984

RESUMO

The S2k guideline "Liver Transplantation", jointly developed by the German Society of Gastroenterology, Digestive and Metabolic Diseases (DGVS) and the German Society of General and Visceral Surgery (DGAV), represents the first German-language guideline for the care of adult patients before and after liver transplantation. This guideline has been crafted through a collaborative, consensus-based approach, involving experts from various disciplines. It integrates current scientific insights and clinical experience to ensure optimal care for patients undergoing liver transplantation. Targeting health care professionals in diagnostics and therapy, patient advocates, affected individuals, and their families, the guideline aims to establish a framework for common decisions in clinical practice.


Assuntos
Gastroenterologia , Transplante de Fígado , Humanos , Consenso , Alemanha
9.
J Clin Invest ; 134(5)2024 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-38227370

RESUMO

Two coding variants of apolipoprotein L1 (APOL1), called G1 and G2, explain much of the excess risk of kidney disease in African Americans. While various cytotoxic phenotypes have been reported in experimental models, the proximal mechanism by which G1 and G2 cause kidney disease is poorly understood. Here, we leveraged 3 experimental models and a recently reported small molecule blocker of APOL1 protein, VX-147, to identify the upstream mechanism of G1-induced cytotoxicity. In HEK293 cells, we demonstrated that G1-mediated Na+ import/K+ efflux triggered activation of GPCR/IP3-mediated calcium release from the ER, impaired mitochondrial ATP production, and impaired translation, which were all reversed by VX-147. In human urine-derived podocyte-like epithelial cells (HUPECs), we demonstrated that G1 caused cytotoxicity that was again reversible by VX-147. Finally, in podocytes isolated from APOL1 G1 transgenic mice, we showed that IFN-γ-mediated induction of G1 caused K+ efflux, activation of GPCR/IP3 signaling, and inhibition of translation, podocyte injury, and proteinuria, all reversed by VX-147. Together, these results establish APOL1-mediated Na+/K+ transport as the proximal driver of APOL1-mediated kidney disease.


Assuntos
Apolipoproteína L1 , Nefropatias , Compostos Organotiofosforados , Camundongos , Animais , Humanos , Apolipoproteína L1/genética , Células HEK293 , Variação Genética , Nefropatias/genética , Camundongos Transgênicos
10.
Z Gastroenterol ; 62(1): 43-49, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38195107

RESUMO

In Germany, organ allocation is based on the MELD-system and lab-MELD is usually low in patients with hepatocellular carcinoma (HCC) in cirrhosis. Higher medical urgency can be achieved by standard exception for HCC (SE-HCC), if Milan criteria (MC) are met. Noteworthy, UNOS T2 reflects MC, but excludes singular lesions < 2 cm. Thus, SE-HCC is awarded to patients with one lesion between 2 and 5 cm or 2 to 3 lesions between 1 and 3 cm. These criteria are static and do not reflect biological properties of HCC.We present a retrospective cohort of 111 patients, who underwent liver transplantation at UKSH, Campus Kiel between 2007 and 2017. No difference was found in overall survival for patient cohorts using Milan, UCSF, up-to-seven, and French-AFP criteria. However, there was a significantly reduced survival, if microvascular invasion was detected in the explanted organ and in patients with HCC-recurrence. The exclusive use of static selection criteria including MC appear to limit the access to liver transplantation.


Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Transplante de Fígado , Humanos , Carcinoma Hepatocelular/diagnóstico , Carcinoma Hepatocelular/cirurgia , Estudos Retrospectivos , Neoplasias Hepáticas/cirurgia , Cirrose Hepática/diagnóstico , Cirrose Hepática/cirurgia
11.
Biochim Biophys Acta Mol Cell Res ; 1871(2): 119529, 2024 02.
Artigo em Inglês | MEDLINE | ID: mdl-37951505

RESUMO

Mitochondria import 1000-1300 different precursor proteins from the cytosol. The main mitochondrial entry gate is formed by the translocase of the outer membrane (TOM complex). Molecular coupling and modification of TOM subunits control and modulate protein import in response to cellular signaling. The TOM complex functions as regulatory hub to integrate mitochondrial protein biogenesis and quality control into the cellular proteostasis network.


Assuntos
Proteínas do Complexo de Importação de Proteína Precursora Mitocondrial , Proteínas Mitocondriais , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Saccharomyces cerevisiae/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo
12.
Psychiatr Prax ; 51(2): 104-109, 2024 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-38159564

RESUMO

The equality of mentally ill people with somatically ill people and the provision of community care were central topics of the Psychiatry-Enquête. With regard to medical rehabilitation services, this goal has not been implemented to date. The amendments to the Ninth Book of the Social Code (SGB IX) made by the Federal Participation Act (BTHG) again open up the possibility of making outreach medical rehabilitation services accessible to people with severe mental illnesses.


Assuntos
Transtornos Mentais , Pacientes Ambulatoriais , Humanos , Alemanha , Psicoterapia , Transtornos Mentais/reabilitação
13.
Child Adolesc Psychiatry Ment Health ; 17(1): 141, 2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38129868

RESUMO

BACKGROUND: Children of families with a parent with a mental illness have an increased risk of developing social and mental health problems resulting in decreased quality of life. Therefore, children and adolescents living in families with a parent with mental illness are regarded as a target group for preventive interventions. To date, only a few economic evaluation studies for interventions directed at preventing the intergenerational transmission of mental health problems exist. In this investigation we estimated the cost utility of an intervention for the support of children and adolescents with a parent having a mental illness from the perspective of the German health and social care system. METHODS: We randomly assigned a total of 214 families with 337 children and adolescents to the intervention (INT) group (108/170) or the control (TAU) group (106/167). Families in the intervention group received on average eight intervention sessions (50-90 min) over 6 months. We estimated total cost of illness by means of the Children and Adolescent Mental Health Service Receipt Inventory (CAMHSRI) over 24 months. For the estimation of Quality-Adjusted Live Years (QALYs) we applied the KIDSCREEN-10. For estimating the incremental cost-utility of the intervention compared to treatment as usual we used the net-benefit approach. RESULTS: We estimated the annual cost of illness amounting to € 3784.59 (SD € 8581.11) in the TAU group and € 3264.44 (SD € 9431.89) in the INT group. The annual cost difference between INT and TAU was € - 516.14 (SE 1124.95) which was not significant (p ≤ 0.05). We estimated the average QALY to be 0.759 (SD 0.073) in the TAU group and 0.763 (SD 0.072). The QALY difference between INT and TAU was 0.0037 (SE 0.0092) which was not significant (p ≤ 0.05). The incremental cost utility ratio (ICUR) indicated that the gain of one additional year in full health by means of the intervention was associated with the saving of € 139.49. However, the stochastic insecurity of the ICUR did not allow a unique decision about the cost-utility of the intervention. CONCLUSIONS: More information on the economic value of the intervention for families with a parent with mental illness in comparison to treatment as usual in Germany is needed. TRIAL REGISTRATION: ClinicalTrials.gov, identifier NCT02308462; German Clinical Trials Register: DRKS00006806.

14.
Trends Cell Biol ; 2023 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-37914576

RESUMO

Mitochondria perform crucial functions in cellular metabolism, protein and lipid biogenesis, quality control, and signaling. The systematic analysis of protein complexes and interaction networks provided exciting insights into the structural and functional organization of mitochondria. Most mitochondrial proteins do not act as independent units, but are interconnected by stable or dynamic protein-protein interactions. Protein translocases are responsible for importing precursor proteins into mitochondria and form central elements of several protein interaction networks. These networks include molecular chaperones and quality control factors, metabolite channels and respiratory chain complexes, and membrane and organellar contact sites. Protein translocases link the distinct networks into an overarching network, the mitochondrial import network (MitimNet), to coordinate biogenesis, membrane organization and function of mitochondria.

15.
Foods ; 12(20)2023 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-37893671

RESUMO

Brewer's spent grain (BSG) is the most abundant residual in the brewing process. Non-starch polysaccharides such as 1,3-1,4-ß-D-glucan (ß-glucan) and arabinoxylan (AX) with proven beneficial effects on human health remain in this by-product in high amounts. Incorporating the valuable dietary fiber into the food industry could contribute to a healthy diet. However, a major challenge is extracting these dietary fibers (i.e., ß-glucan and AX) from the solid residue. In this study, hydrothermal treatment (HT) was applied to dissolve the remaining water-insoluble carbohydrates from BSG with the aim to extract high amounts of ß-glucan and AX. Particular focus was placed on the molecular weight (MW) range above 50 kDa and 20 kDa, respectively, as these are considered to have health-promoting effects. Different treatment temperatures, reaction times, and internal reactor pressures were tested to determine the best process settings to achieve high yields of ß-glucan and AX and to examine the influence on their molecular weight distribution (MWD). Overall, 85.1% ß-glucan and 77.3% AX were extracted corresponding to 6.3 g per kg BSG at 160 °C and 178.3 g kg-1 at 170 °C, respectively. However, less than 20% of both fiber substances were in the desirable MW range above 50 kDa and 20 kDa, respectively. When lower temperatures of 140 and 150 °C were applied, yields of only 3.0 g kg-1 ß-glucan and 128.8 g kg-1 AX were obtained, whereby the proportion of desirable fiber fractions increased up to 45%. Further investigations focused on the heat-induced degradation of monosaccharides and the formation of undesirable by-products (i.e., HMF and furfural) that might pose a health risk.

16.
Psychiatr Prax ; 2023 Oct 09.
Artigo em Alemão | MEDLINE | ID: mdl-37813363

RESUMO

OBJECTIVE: The influence of guideline recommendations and other factors on the utilization of psychosocial interventions in people with severe mental illness was examined. METHODS: Data from a cross-sectional study of 397 people with severe mental illness were analysed descriptively. RESULTS: Patients are less likely to receive therapies with a strong recommendation compared to other levels of recommendation. Various other factors are diffusely associated with utilization rates, but no ubiquitous predictors could be identified across all therapies. CONCLUSION: Current practice in the use of psychosocial interventions does not follow guideline recommendation strength. Interventions with strong recommendations are probably not available across services. Consequently, routine practice is not able to follow guideline recommendations according to their strength. Other consistent predictors could not be identified.

17.
Nat Metab ; 5(11): 1931-1952, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37813994

RESUMO

Reversible acetylation of mitochondrial proteins is a regulatory mechanism central to adaptive metabolic responses. Yet, how such functionally relevant protein acetylation is achieved remains unexplored. Here we reveal an unprecedented role of the MYST family lysine acetyltransferase MOF in energy metabolism via mitochondrial protein acetylation. Loss of MOF-KANSL complex members leads to mitochondrial defects including fragmentation, reduced cristae density and impaired mitochondrial electron transport chain complex IV integrity in primary mouse embryonic fibroblasts. We demonstrate COX17, a complex IV assembly factor, as a bona fide acetylation target of MOF. Loss of COX17 or expression of its non-acetylatable mutant phenocopies the mitochondrial defects observed upon MOF depletion. The acetylation-mimetic COX17 rescues these defects and maintains complex IV activity even in the absence of MOF, suggesting an activatory role of mitochondrial electron transport chain protein acetylation. Fibroblasts from patients with MOF syndrome who have intellectual disability also revealed respiratory defects that could be restored by alternative oxidase, acetylation-mimetic COX17 or mitochondrially targeted MOF. Overall, our findings highlight the critical role of MOF-KANSL complex in mitochondrial physiology and provide new insights into MOF syndrome.


Assuntos
Fibroblastos , Mitocôndrias , Humanos , Animais , Camundongos , Acetilação , Fibroblastos/metabolismo , Mitocôndrias/metabolismo , Metabolismo Energético , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Proteínas de Transporte de Cobre/metabolismo
18.
Polymers (Basel) ; 15(19)2023 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-37836008

RESUMO

Water-extractable arabinoxylan (WEAX) may cause major problems during clarification processes in a brewery owing to its ability to form gel networks. However, high WEAX contents can also enhance the nutritional quality of the final product as they play an important role in the human diet. Therefore, precise quantification of WEAX is required. Current methods are very time- and resource-consuming as well as limited in the number of samples and in some cases provide low accuracy. Thus, a reproducible high-throughput method for the quantification of WEAX optimized for beer was developed, reaching recovery rates (RRs) of almost 100%. The assay is based on Douglas's colorimetric method. Hydrolysis was conducted using glacial acetic acid to induce the formation of red color complexes resulting from the interaction between pentose degradation products and phloroglucinol. The method was successfully transferred to a multi-mode microplate reader to minimize the loss of color intensity over time and to obtain a high throughput. By using 96-well plates, up to 40% of the previous analysis time could be saved, and a larger number of samples could be analyzed in one batch. The collected data determined xylose as an optimal calibration standard due to high accuracy and reproducibility. The respective AX control standards showed RR within the range of 95-105% without exception. To validate and show the ruggedness of the modified method, WEAX concentration in seven commercial German beers (e.g., lager, pilsner, wheat beer, non-alcoholic beer) was quantified. Interfering hexose sugars that lead to measurement errors when analyzing samples with high amounts of fermentable sugars (e.g., non-alcoholic beer produced by limited fermentation) were eliminated by Saccharomyces diastaticus fermentation. Further investigations were carried out by means of LC-MS in order to obtain additional information about the reddish product in the hydrolyzed samples. In this context, C16H12O6 could be identified as one of numerous condensation products, contributing to the coloring. The collected data showed the impact of diverse factors on the measured AX concentration and helped optimize the experimental procedure for a high sample throughput with precise and highly reproducible results. The proposed quantification method should be primarily used in completely fermented finished beer to emphasize the time aspect. Wort samples and non-alcoholic beer produced by limited fermentation can be also analyzed, but only after fermentation with S. diastaticus.

19.
J Texture Stud ; 54(6): 926-935, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37605805

RESUMO

A comprehensive in-situ analysis of the developing gluten network during kneading is still a gap in cereal science. With an in-line microscale shear kneading and measuring setup in a conventional rheometer, a first step was taken in previous works toward fully comprehensible gluten network development evaluation. In this work, this setup was extended by an in-situ optical analysis of the evolving gluten network. By connecting a laser scanning microscope with a conventional rheometer, the evaluation of the rheological and optical protein network evolution was possible. An image processing tool for analyzing the protein network was applied for evaluating the gluten network development in a wheat dough during the shear kneading process. This network evaluation was possible without interruption or invasive sample transfer comparing it to former approaches. The shear kneading system was able to produce a fully developed dough matrix within 125% of the reference dough development time in a classical kneader. The calculated network connectivity values from frequency testing ranged over all samples was in good agreement with traditional kneaded wheat dough just over peak consistency.


Assuntos
Farinha , Glutens , Farinha/análise , Microscopia Confocal , Triticum , Reologia
20.
Polymers (Basel) ; 15(16)2023 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-37631499

RESUMO

Vital gluten is increasingly researched as a non-food product for biodegradable materials. During processing, the protein network is confronted with increased thermal and mechanical stress, altering the network characteristics. With the prospect of using the protein for materials beyond food, it is important to understand the mechanical properties at various processing temperatures. To achieve this, the study investigates hydrated vital gluten under thermomechanical stress based on large amplitude oscillatory shear (LAOS) rheology. LAOS rheology was conducted at increasing shear strains (0.01-100%), various frequencies (5-20 rad/s) and temperatures of 25, 45, 55, 65, 70 and 85 °C. With elevating temperatures up to 55 °C, the linear viscoelastic moduli decrease, indicating material softening. Then, protein polymerization and the formation of new cross-links due to thermal denaturation cause more network connectivity, resulting in significantly higher elastic moduli. Beyond the linear viscoelastic regime, the strain-stiffening ratio rises disproportionately. This effect becomes even more evident at higher temperatures. Lacking a viscous contribution, the highly elastic but also stiff network shows less mechanical resilience. Additionally, at these elevated temperatures, structural changes during the protein's denaturation and network shrinkage due to water evaporation could be visualized with confocal laser scanning microscopy (CLSM).

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