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Publisher Copyright: © 2021 Institute of Food Technologists® Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice–water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.

Protein oxidation readily occurs in postmortem muscle during storage and processing. Over the past decade new analytical methods have been developed and new aspects of protein oxidation in meat have been studied, such as the reaction mechanism, and impacts on eating quality and nutritional value. It is now evident that amino acid side chains in myofibrillar proteins undergoes modifications due to oxidative stress. In turn this will lead to formation of new protein-protein cross-links in structural proteins, however, also the overall level of fixed-charge groups attached to the peptide backbones is modified. Meat texture and water-holding are important quality attributes and they are affected by the oxidation of structural proteins. Different mechanisms have been suggested to explain the oxidation-induced quality changes, focusing mainly on reduced proteolysis and formation of cross-links. This review explores the current understanding of protein oxidation in fresh meat in relation to texture and water-holding. The consequences of protein oxidation at molecular level in relation to oxidation-induced cross-linking and changes in net charges of myofibrillar proteins, and the impacts on texture and water-holding are discussed.

Background Exploration of the genes with abnormal expression during the development of breast cancer is essential to provide a deeper understanding of the mechanisms involved. Transcriptome sequencing and bioinformatics analysis of invasive ductal carcinoma and paracancerous tissues from the same patient were performed to identify the key genes and signaling pathways related to breast cancer development. Methods Samples of breast tumor tissue and paracancerous breast tissue were obtained from 6 patients. Sequencing used the Illumina HiSeq platform. All. Only perfectly matched clean reads were mapped to the reference genome database, further analyzed and annotated based on the reference genome information. Differentially expressed genes (DEGs) were identified using the DESeq R package (1.10.1) and DEGSeq R package (1.12.0). Using KOBAS software to execute the KEGG bioinformatics analyses, enriched signaling pathways of DEGs involved in the occurrence of breast cancer were determined. Subsequently, quantitative real time PCR was used to verify the accuracy of the expression profile of key DEGs from the RNA-seq result and to explore the expression patterns of novel cancer-related genes on 8 different clinical individuals. Results The transcriptomic sequencing results showed 937 DEGs, including 487 upregulated and 450 downregulated genes in the breast cancer specimens. Further quantitative gene expression analysis was performed and captured 252 DEGs (201 downregulated and 51 upregulated) that showed the same differential expression pattern in all libraries. Finally, 6 upregulated DEGs (CST2, DRP2, CLEC5A, SCD, KIAA1211, DTL) and 6 downregulated DEGs (STAC2, BTNL9, CA4, CD300LG, GPIHBP1 and PIGR), were confirmed in a quantitative real time PCR comparison of breast cancer and paracancerous breast tissues from 8 clinical specimens. KEGG analysis revealed various pathway changes, including 20 upregulated and 21 downregulated gene enrichment pathways. The extracellular matrix–receptor (ECM-receptor) interaction pathway was the most enriched pathway: all genes in this pathway were DEGs, including the THBS family, collagen and fibronectin. These DEGs and the ECM-receptor interaction pathway may perform important roles in breast cancer. Conclusion Several potential breast cancer-related genes and pathways were captured, including 7 novel upregulated genes and 76 novel downregulated genes that were not found in other studies. These genes are related to cell proliferation, movement and adhesion. They may be important for research into breast cancer mechanisms, particularly CST2 and CA4. A key signaling pathway, the ECM-receptor interaction signal pathway, was also identified as possibly involved in the development of breast cancer. Electronic supplementary material The online version of this article (10.1186/s11658-019-0162-0) contains supplementary material, which is available to authorized users.

The aim of the thesis was to investigate the effects and mechanisms of protein oxidation on meat quality traits, such as texture, color and water-holding properties. To achieve this, meat was subjected to modified atmosphere packaging (MAP) with different oxygen concentrations and protein oxidation as well as meat quality traits (with a focus on texture and color) were measured. In addition, a model system of HClO-oxidized myofibrils was used to study the effect of protein oxidation on filament net charges, protein aggregation and their relation to water-holding. Generally, protein oxidation was found to increase significantly both with increasing oxygen concentrations in MAP and with increasing concentrations of the oxidant HClO. Lipid oxidation, measured as TBARS, was also greater in meat stored under higher oxygen atmosphere. Shear force of porcine longissimus dorsi (LD) muscle increased with increasing oxygen concentrations demonstrating a meat toughening effect. The role of proteolysis and protein cross-linking on oxidation-induced toughening was investigated. Myosin heavy chain (MHC) cross-linking was greater in 80% oxygen MAP than 0% and 20% oxygen, while desmin degradation was not affected by the oxygen concentrations in MAP, suggesting that oxidation-induced toughening was due to cross-linking of structural proteins rather than reduced proteolysis. Oxidation-induced toughening was also observed in minced beef as the hardness was generally greater in patties made from meat stored under 20-80% oxygen compared to 0% oxygen. The internal redness of cooked patties decreased with increasing cooking temperatures and increasing oxygen concentrations in MAP, and a relative low oxygen concentration of 20% was able to cause premature browning (e.g., the patties made from 20% oxygen packaged meat showed brown cooked appearance at 55 ºC while 0% oxygen led to pink-red color). In the model system, water-holding was generally improved by oxidation. Protein cross-linking was evidenced by increasing particle size with increasing concentrations of HClO. Isoelectric focusing (IEF) showed that the isoelectric point (pI) of solubilized myofibrillar proteins were generally lower following oxidation, indicating an increase of net negative charge. In the thesis, a hypothesis about oxidation-induced changes and their relation to water-holding is proposed: The oxidation-induced increase of net negative charges is due to loss of positively charged histidine residues through protein carbonylation, and water-holding is a balance between promoting factors (e.g., increased net charge) and inhibiting factors (e.g., cross-linking and aggregation). Väitöskirjan tavoite oli tutkia proteiinien hapettumisen vaikutuksia ja vaikutusmekanismeja lihan laatuominaisuuksiin, kuten mureuteen, väriin ja vedenpidätyskykyyn eli lihan kykyyn pidättää lihasnestettä. Tätä varten lihaa säilytettiin suojakaasupakkauksissa eri happipitoisuuksissa. Tutkimuksessa mitattiin proteiinien hapettumista sekä eräitä lihan laatuominaisuuksia, erityisesti mureutta ja väriä. Lisäksi myofibrilliproteiineja hapetettiin mallikokeissa hypokloriittihapolla (HClO) ja tutkittiin sitten proteiinien hapettumisen vaikutusta filamenttien nettovarauksiin, proteiinien yhteenliittymiseen ja näiden seikkojen vaikutuksia vedenpidätyskykyyn. Yleisesti ottaen proteiinien hapettumisen todettiin lisääntyvän sekä suojakaasupakkausten happipitoisuuden että HClO-pitoisuuden noustessa. TBARS-arvoina mitattu rasvojen hapettuminen oli myös suurempaa, kun liha oli säilytetty korkeammissa happipitoisuuksissa. Proteolyysin ja proteiinien poikkisidosten merkitystä tutkittiin hapettumisen aiheuttaman sitkeyden kannalta. Sian longissimus dorsi -lihaksen leikkautumisvoima kasvoi suojakaasun happipitoisuuden noustessa, mikä osoitti lihan sitkeyden lisääntymistä. Myosiinin raskaan ketjun poikittaissidosten määrä oli suurempi 80 % happea sisältävissä kuin 0 tai 20 % sisältävissä suojakaasupakkauksissa, kun taas pakkausten happipitoisuus ei vaikuttanut desmiinin tuhoutumiseen, mikä viittaa siihen, että hapettumisen aiheuttaman sitkistyminen johtuu pikemminkin poikittaissidosten muodostumisesta kuin proteolyysin vähenemisestä. Hapettumisen aiheuttama sitkistymistä havaittiin myös jauhelihassa, koska 20-80 %:in happipitoisuudessa säilytetystä lihasta valmistetut jauhelihapihvit olivat kovempia kuin 0 %:in happipitoisuudessa säilytetyistä lihoista valmistetut. Jauhelihapihvien sisällä värin punaisuus laski kypsennyslämpötilan ja suojakaasupakkauksen happipitoisuuden noustessa, ja jo melko matala happipitoisuus (20 %) aiheutti ns. ennenaikaisen ruskistumisen. Esimerkiksi 20 %:in happipitoisuudessa säilytetystä lihasta valmistetut jauhelihapihvit olivat sisältä ruskeita 55 °C:eessa, kun taas 0 %:issa säilytetyissä lihoista valmistetut olivat sisältä vaaleanpunaisia. Mallikokeessa proteiinien poikittaissidosten muodostuminen voitiin osoittaa proteiinipartikkelien koon kasvun kautta HClO-pitoisuuden kasvaessa, mutta hapettuminen silti paransi vedenpidätyskykyä. Isoelektrisen fokusointimenetelmän avulla voitiin osoittaa, että liuenneiden myofibrilliproteiinien isoelektrinen piste laski hapettumisen seurauksena. Tämä osoittaa negatiivisen nettovarauksen kasvua. Väitöskirjassa esitetään hypoteesi hapettumisen aiheuttamista muutoksista vedensidontakykyyn: koska vedenpidätyskyvyn muutos on tasapainossa edistävien tekijöiden (esim. nettovarauksen kasvu) ja estävien tekijöiden (esim. poikittaissidokset ja proteiinien yhteenliittyminen) välillä ja koska hapettumisen aiheuttama negatiivisten nettovarauksen nousu johtuu positiivisesti varautuneen histidiinin sivuketjun neutraloitumisesta proteiinien karbonylaation seurauksena, vedenpidätyskyvyn nousun katsottiin johtuvan histidiinin hapettumisesta.

The complete mitochondrial genome of the hybrid of Takifugu obscurus (♀) × Takifugu rubripes (♂) was sequenced and characterized in this study. The hybrid mitochondrial DNA, with a total length of 16,443 bp, contain 37 genes, including 13 protein-coding genes, 22 tRNAs genes, and 2 rRNA gene. There are two noncoding regions: the origin of light-strand replication (OL) and control region (D-loop). The complete mitochondrial genome of the hybrid of T. obscurus (♀) × T. rubripes (♂) provides data for studies on genetic diversity and species identification among Takifugu.

This paper presents two approaches for the structural damage identification of a bridge from the dynamic response recorded from a test vehicle during its passage over the bridge. Using the acceleration response recorded by the vibration sensors mounted on a test vehicle during its passage over the bridge, along with the computed displacement response, the bending stiffness of the bridge can be determined using either: (1) the frequency-domain method based on the improved directed stiffness method with the identified frequency and corresponding mode shape, or (2) the time-domain method based on the residual vector of the least squares method with a fourth-order displacement moment. By comparing the bending stiffness values identified from the vehicle-collected data for the bridge under the undamaged and damaged states that are monitored regularly by the test vehicle, the bridge damage location and severity can be identified. Through numerical simulations and field tests, the present approaches are shown to be effective and feasible.