ФИЗИЧЕСКИЕ ХАРАКТЕРИСТИКИ КАЗЕИНА ПРИ ОБРАБОТКЕ ВЫСОКИМ ДАВЛЕНИЕМ В РАСТВОРЕ

The aim of this work was to study the effect of pressure (50; 90; 160; 250; 350 MPa) on a physical property of casein micelle: hydrodynamic radius, tyrosine and tryptophan fluorescence and IR spectra characteristics. According to photon-correlation spectroscopy, the average hydrodynamic radius of the casein micelle was 128 nm, increasing at 50 MPa to 467 nm with the formation of conglomerates. Further increase of pressure led to the formation of two fractions of particles, differing in hydrodynamic radius. At a pressure of 350 MPa, an average radius of 75 % of particles was 121 nm. Comparison of hydrodynamic radius and tyrosine fluorescence revealed a decrease in the intensity of the glow with an increase in the proportion of large particles and an increase in the radiation in the solution with a decrease of the micelles size. The increase of casein fluorescence by tryptophan and its decrease by tyrosine indicate a change in the conformation of protein molecules during pressure treatment. FTIR spectroscopy revealed a change in the intensity of the optical density in the range of amide I, amide II and valence bonds of tyrosine, confirming the absence of new bonds. The obtained physical data indicate a change in the structure of casein micelles with an increase in the proportion (25 %) of large particles after the action of high pressure (350mpa), which should be taken into account in milk processing. The fluorescence of casein during pressure treatment is a poorly investigated physical indicator and can be important for the processing of raw milk.Целью данного исследования было изучение влияния воздействия давления (50; 90; 160; 250; 350 МПа) на ряд физических свойств мицеллы казеина: гидродинамический радиус, флюоресценцию тирозина и триптофана и характеристику ИК-спектров. По данным фотонно-корреляционной спектроскопии средний гидродинамический радиус мицеллы казеина составил 128 нм, увеличиваясь при 50 МПа до 467 нм с образованием конгломератов. Дальнейшее увеличение давления привело к формированию двух фракций частиц, различающихся по величине гидродинамического радиуса. При давлении в 350 МПа основную часть (75 %) составляли частицы со средним радиусом 121 нм. Сопоставление гистограмм гидродинамического радиуса и флуоресценции тирозина обнаружило снижение интенсивности свечения при увеличении доли частиц больших размеров и рост излучения в растворе при уменьшении размера мицелл. Рост флуоресценции казеина по триптофану и её снижение по тирозину указывают на изменение конформации белковых молекул при обработке давлением. ИК-Фурье спектроскопия выявила изменение интенсивности оптической плотности в диапазоне амид I, амид II и валентных связей тирозина, подтверждая отсутствие появления новых связей.Полученные физические данные указывают на изменение структуры казеиновых мицелл с увеличением доли (25 %) крупных частиц после действия высокого давления (350МПа), что следует учитывать в переработке молока. Флюоресценция казеина при обработке давлением является слабо исследованным физическим показателем и может нести прикладное значение для технологической обработки молочного сырья

A Review of Evidence for the Involvement of the Circadian Clock Genes into Malignant Transformation of Thyroid Tissue

(1) Background: In 2013, the results of a pioneer study on abnormalities in the levels and circadian rhythmicity of expression of circadian clock genes in cancerous thyroid nodules was published. In the following years, new findings suggesting the involvement of circadian clockwork dysfunction into malignant transformation of thyroid tissue were gradually accumulating. This systematic review provides an update on existing evidence regarding the association of these genes with thyroid tumorigenesis. (2) Methods: Two bibliographic databases (Scopus and PubMed) were searched for articles from inception to 20 March 2023. The reference lists of previously published (nonsystematic) reviews were also hand-searched for additional relevant studies. (3) Results: Nine studies published between 2013 and 2022 were selected. In total, 9 of 12 tested genes were found to be either up- or downregulated. The list of such genes includes all families of core circadian clock genes that are the key components of three transcriptional–translational feedback loops of the circadian clock mechanism (BMAL1, CLOCK, NPAS2, RORα, REV-ERBα, PERs, CRYs, and DECs). (4) Conclusions: Examination of abnormalities in the levels and circadian rhythmicity of expression of circadian clock genes in thyroid tissue can help to reduce the rate of inadequate differential preoperative diagnosis for thyroid carcinoma

The Irrecoverable Loss in Sleep on Weekdays of Two Distinct Chronotypes Can Be Equalized by Permitting a >2 h Difference in Waking Time

Background: Our work/study culture is biased towards the circadian clocks of “morning types”, whereas “evening types” are forced to advance their weekday waking times relative to weekend waking times. Since the experimental research consistently reveals a >2 h difference between these two chronotypes in the positions of their endogenous circadian phases, we hypothesized the necessity to permit a >2 h difference between them in weekday waking times to equalize their irrecoverable loss in sleep on weekdays. Methods: A total of 659 and 1106 participants of online surveys identified themselves as morning and evening types, respectively. The hypothesis was tested by applying a model of sleep–wake regulation for simulating sleep times reported by 245 lecturers of these two types, and by comparison of sleep times of these types among these lecturers and 1520 students. Results: The hypothesis was supported by results showing that, if, on weekdays, an “average” morning type wakes at 6 a.m., the equalization of the weekday sleep loss of the two chronotypes would require the waking time of an “average” evening type to be no earlier than 8 a.m. Conclusions: These results may be implemented in a model-based methodology for the correction of weekday waking times to equalize weekday sleep loss