The effects of chain-length distributions on starch-related properties in waxy rices.

Normal rice starch consists of amylopectin and amylose, whose relative amounts and chain-length distributions (CLDs) are major determinants of the digestibility and rheology of cooked rice, and are related to metabolic health and consumer preference. Here, the mechanism of how molecular structural features of pure amylopectin (waxy) starches affect starch properties was explored. Following debranching, chain-length distributions of seven waxy varieties were measured using size-exclusion chromatography, and parameterized using biosynthesis-based models, which involve breaking up the chain-length distribution into contributions from five enzyme sets covering overlapping ranges of chain length; structure-property correlations involving the fifth set were found to be statistically significant. Digestibility was measured in vitro, and parameters for the slower and longer digestion phase quantified using non-linear least-squares fitting. The coefficient for the significant correlation involving amylopectin fine structure for the fifth set was -0.903, while the amounts of amylopectin short and long chains were found to dominate breakdown viscosity (correlation coefficients 0.801 and - 0.911, respectively). This provides a methodology for finding or developing healthier starch in terms of lower digestion rate, while also having acceptable palatability. As rice breeders can to some extent control CLDs, this can help the development of waxy rices with improved properties.

Insights into wheat-starch biosynthesis from two-dimensional macromolecular structure.

Starch structure is often characterized by the chain-length distribution (CLD) of the linear molecules formed by breaking each branch-point. More information can be obtained by expanding into a second dimension: in the present case, the total undebranched-molecule size. This enables answers to questions unobtainable by considering only one variable. The questions considered here are: (i) are the events independent which control total size and CLD, and (ii) do ultra-long amylopectin (AP) chains exist (these chains cannot be distinguished from amylose chains using simple size separation). This was applied here to characterize the structures of one normal (RS01) wheat and two high-amylose (AM) mutant wheats (an SBEIIa knockout and an SBEIIa and SBEIIb knockout). Absolute ethanol was used to precipitate collected fractions, then size-exclusion chromatography for total molecular size and for the size of branches. The SBEIIa and SBEIIb mutations significantly increased AM and IC contents and chain length. The 2D plots indicated the presence of small but significant amounts of long-chain amylopectin, and the asymmetry of these plots shows that the corresponding mechanisms share some causal effects. These results could be used to develop plants producing improved starches, because different ranges of the chain-length distribution contribute independently to functional properties.

Using molecular fine structure to identify optimal methods of extracting fungal glycogen.

Glycogen is a highly branched glucose polymer that is an energy storage material in fungi and animals. Extraction of glycogen from its source in a way that minimizes its molecular degradation is essential to investigate its native structure. In this study, the following extraction methods were compared: sucrose gradient density ultracentrifugation, thermal alkali, hot alcohol and hot water extractions. Molecular-size and chain-length distributions of glycogen were measured by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis, respectively. These two fine-structure features are the most likely structural characteristics to be degraded during extraction. The results show that the thermal alkali, hot alcohol and hot water extractions degrade glycogen molecular size and/or chain-length distributions, and that sucrose gradient density ultracentrifugation with neither high temperature nor alkaline treatment is the most suitable method for fungal glycogen extraction.

Normal and abnormal glycogen structure - A review.

Glycogen, a complex branched glucose polymer, is found in animals and bacteria, where it serves as an energy storage molecule. It has linear (1 â†’ 4)-α glycosidic bonds between anhydroglucose monomer units, with branch points connected by (1 â†’ 6)-α bonds. Individual glycogen molecules are referred to as ß particles. In organs like the liver and heart, these ß particles can bind into larger aggregate α particles, which exhibit a rosette-like morphology. The mechanisms and bonding underlying the aggregation process are not fully understood. For example, mammalian liver glycogen has been observed to be molecularly fragile under certain conditions, such as glycogen from diabetic livers fragmenting when exposed to dimethyl sulfoxide (DMSO), while glycogen from healthy livers is much less fragile; this indicates some difference, as yet unknown, in the bonding between ß particles in healthy and diabetic glycogen. This fragility may have implications for blood sugar regulation, especially in pathological conditions such as diabetes.

Liver glycogen fragility in the presence of hydrogen-bond breakers.

Glycogen, a complex branched glucose polymer, is responsible for sugar storage in blood glucose homeostasis. It comprises small ß particles bound together into composite α particles. In diabetic livers, α particles are fragile, breaking apart into smaller particles in dimethyl sulfoxide, DMSO; they are however stable in glycogen from healthy animals. We postulate that the bond between ß particles in α particles involves hydrogen bonding. Liver-glycogen fragility in normal and db/db mice (an animal model for diabetes) is compared using various hydrogen-bond breakers (DMSO, guanidine and urea) at different temperatures. The results showed different degrees of α-particle disruption. Disrupted glycogen showed changes in the mid-infra-red spectrum that are related to hydrogen bonds. While glycogen α-particles are only fragile under harsh, non-physiological conditions, these results nevertheless imply that the bonding between ß particles in α particles is different in diabetic livers compared to healthy, and is probably associated with hydrogen bonding.

A retrospective comparison of postoperative outcomes in ovariectomised jennies (Equus asinus) treated with phenylbutazone or flunixin meglumine.

BACKGROUND: Clinically, flunixin meglumine (FM) and phenylbutazone (PBZ) are preferentially selected for the treatment of visceral and musculoskeletal pain, respectively, in horses. In donkeys, there is no information to support or refute this conventional conjecture. OBJECTIVES: To compare postoperative outcomes in a group of jennies treated with intravenous FM or oral PBZ. ANIMALS: Fourteen jennies unilaterally ovariectomised by standing left flank laparotomy. STUDY DESIGN: Retrospective cohort study. METHODS: Data from medical records of ovariectomised jennies (case details, weight, non-steroidal anti-inflammatory drug [NSAID] protocol, surgery duration, operative sequence, anaesthesia protocol, physical examination findings and outcomes) were collected. From collated data, postoperative adverse events were defined as fever, tachycardia, tachypnea, inappetence, altered mentation, abnormal oral mucous membranes, bruxism, colic, incisional complications (i.e., drainage, oedema, peri-incisional emphysema and pain) and non-survival, then further divided into occurrence during the early (≤24 h) or late (>24 h) postoperative period for data analysis using R software. Chi-squared test was used to compare individual adverse events between groups (PBZ vs. FM) and moments (early vs. late). Significance was set at p ≤ 0.05. RESULTS: PBZ treatment (8/14) was associated with (odds ratio, 95% confidence interval) more total (2.93, 1.97-4.36), early (3.01, 1.87-4.84) and late (2.69, 1.28-5.63) adverse events than FM treatment (6/14). Tachycardia (37.83, 2.21-646.66), tachypnoea (0.29, 0.13-0.66), altered mentation (2.78, 1.01-7.67), altered mucous membranes (18.38, 1.04-325.23), incisional oedema (44.33, 2.60-754.5) and incisional pain (47.78, 2.81-811.61) were significantly different between groups. Early adverse events significantly different between groups included tachycardia (50.2, 2.9-877.0), altered mentation (3.33, 1.08-10.29) and incisional pain (21.0, 1.2-374.5), with late adverse events being tachypnea (0.07, 0.01-0.62), incisional oedema (32.92, 1.85-584.28) and incisional pain (28.92, 1.62-515.68). Colic (2/8) and non-survival (1/8) were rare events that only occurred in the PBZ cohort and could not be further evaluated for differences. MAIN LIMITATIONS: Small sample size; retrospective study; treatment bias; varied administration routes. CONCLUSIONS: Oral PBZ may be inappropriate to use following abdominal surgery in donkeys. CLINICAL RELEVANCE: More prospective and case-controlled studies are needed to evaluate the clinical efficacy of these two NSAIDs in donkeys.

Formation mechanism of α particles in glycogen: Testing the budding hypothesis by Monte-Carlo simulation.

Glycogen, a complex branched glucose polymer and a blood-sugar reservoir in animals, comprises small ß particles joined together into composite α particles. In diabetic animals, α particles fragment more easily than those in healthy animals. Finding evidence for or against postulated mechanisms for α-particle formation is thus important for diabetes research. Insight into this is obtained here using Monte-Carlo simulations, including addition and loss of glucose monomer, branching and debranching, based on earlier simulations which were in acceptable agreement with experiment [Zhang et al., Int J Biol Macromolecules 2018, 116, 264]. One postulated mechanism for α-particle formation is "budding": occasionally a glucan chain temporarily protrudes from the particle, and if its growing end is sufficiently far from its parent particle, it propagates to a new linked particle. We tested this by simulations in which an "artificial" bud (a chain extending well outside the average particle radius) is added to a glycogen molecule in a dynamic steady state, and the system allowed to evolve. In some simulations, the particle reached a new steady state having an irregular dumbbell shape: a rudimentary α particle. Thus 'budding' is a possible mechanism for α particles to form. If no simulations had shown this behaviour, it would have refuted the postulate.

Clinical value of whole body 18F-FDG PET/CT imaging in patients with cutaneous melanoma: A multi-center cohort study.

BACKGROUND: 18F-FDG-PET/CT is a valuable tool in the staging and surveillance of cutaneous melanoma; however, recent studies prompt debate on the clinical significance of imaging patients below the lesser trochanter. This study explored two research questions. In patients with a known primary cutaneous melanoma within the standard field of view (SFOV, between the orbits and lesser trochanter), what is the prevalence of metastasis to sites solely within the lower extremities? and, In patients with a known primary cutaneous melanoma within the SFOV what demographic and clinical factors are associated with sole metastasis to the lower extremities? METHODS: A retrospective, multi-centered, observational study of consecutive case reports was conducted. Subjects included 619 patients who underwent extended field of view (EFOV) 18F-FDG-PET/CT (from vertex to toes) for staging and/or follow-up of cutaneous melanoma. Data was collected at three primary healthcare centers in Canada (Nova Scotia, Alberta, and British Columbia). Inclusion criteria were patients >18 years of age, confirmed primary cutaneous melanoma, and a known location of the primary within the SFOV. Patients with primary cutaneous melanoma lesions in lower extremities and previous other cancers were excluded. To determine the prevalence of lesions located below the lesser trochanter, the proportion of such lesions were computed, and 95% confidence intervals ensured a precise estimation of the proportion. RESULTS: 2512 patient charts were reviewed with 619 meeting the inclusion criteria, 298 of these were females. Six percent had metastases in both the lower extremities and sites within the SFOV. The number of subjects who had no metastasis within their SFOV was 361 (58.3%). The number of subjects who presented with confirmed metastasis in the lower extremities without concurrent metastasis in the SFOV region was one (0.58%). Despite a large initial study sample, the number of patients with metastasis in the lower extremities was insufficient to allow correlation of factors associated with risk of spread to the lower extremities. CONCLUSION: Lower extremity 18F-FDG-PET/CT provided additional, relevant clinical data in a sole patient. This finding supports prior research suggesting the prevalence is rare. Future studies should seek to define demographic and clinical factors that predict such rare occurrences, where follow up would be warranted. This study highlights feasibility challenges associated with such investigation.

Influence of Storage Temperature on Starch Retrogradation and Digestion of Chinese Steamed Bread.

Chinese steamed bread (CSB), which is widely consumed in East Asia, usually undergoes storage before consumption, but it is unclear how different storage temperatures affect CSB starch retrogradation and digestion properties, which are important for consumers. CSB was stored for 2 days at 25 °C, 4 °C, -18 °C, 4 °C/25 °C temperature cycling (i.e., 24 h at 4 °C, followed by 24 h at 25 °C) and -18 °C/ 25 °C temperature cycling. The results revealed for the first time that more orderly starch double helices are formed when CSB was stored at 4 °C or 4 °C/25 °C. Storage under -18 °C produced lower amounts of, but more heterogenous, starch double helices, with fewer B-type, but more V-type, crystallites. Compared to other storage temperatures, more long-range intermolecular interactions formed between the starch and protein at 4 °C or 4 °C/25 °C. CSB samples showed the slowest starch digestibility when stored at 4 °C. The impact of storage temperature on the starch retrogradation properties and digestibility of CSB also depended on the wheat variety, attributed to differences in the starch molecular structure. These results have significance and practical applications to help the CSB food industry to control starch retrogradation and digestibility. For example, CSB could be stored at 4 °C for 2 days in order to reduce its starch digestibility.

Automatic montaging of adaptive optics SLO retinal images based on graph theory.

We present a fully automatic montage pipeline for adaptive optics SLO retinal images. It contains a flexible module to estimate the translation between pairwise images. The user can change modules to accommodate the alignment of the dataset using the most appropriate alignment technique, provided that it estimates the translation between image pairs and provides a quantitative confidence metric for the match between 0 and 1. We use these pairwise comparisons and associated metrics to construct a graph where nodes represent frames and edges represent the overlap relations. We use a small diameter spanning tree to determine the best pairwise alignment for each image based on the entire set of image relations. The final stage of the pipeline is a blending module that uses dynamic programming to improve the smoothness of the transition between frames. Data sets ranging from 26 to 119 images were obtained from individuals aged 24 to 81 years with a mix of visually normal control eyes and eyes with glaucoma or diabetes. The resulting automatically generated montages were qualitatively and quantitatively compared to results from semi-automated alignment. Data sets were specifically chosen to include both high quality and medium quality data. The results obtained from the automatic method are comparable or better than results obtained by an experienced operator performing semi-automated montaging. For the plug-in pairwise alignment module, we tested a technique that utilizes SIFT + RANSAC, Normalized cross-correlation (NCC) and a combination of the two. This pipeline produces consistent results not only on outer retinal layers, but also on inner retinal layers such as a nerve fiber layer or images of the vascular complexes, even when images are not of excellent quality.

Subtle structural variations of resistant starch from whole cooked rice significantly impact metabolic outputs of gut microbiota.

While cooked rice is widely consumed as a whole food, the specific characteristics and impact of its resistant starch (RS) on gut microbiota are largely unexplored. In this study, three rice varieties with distinct starch molecular structures were used to prepare RS from cooked rice. All three types of RS had a crystalline structure characterized as B + V type, with the V type being the predominant crystalline polymorph. Distinct differences in chain-length distributions were observed among different RSs, with rapidly fermentable starch fractions comprising short amylopectin and long amylose chains, while the degrees of polymerization (DPs) âˆ¼ 10, 37, 65, and 105 fractions comprised the slowly fermentable starch. Jasmine rice RS showed the highest proportion of this slowly fermentable starch fraction, which appeared to be specifically utilized by Megasphaera_elsdenii_DSM_20460 OTU198. The fermentation of Jasmine RS resulted in the highest production of butyrate after 24 h, which was positively correlated with the relative abundance of Megasphaera_elsdenii_DSM_20460 OTU198. These findings collectively indicate that RS in cooked rice with a higher V type crystallinity and DPs âˆ¼ 10, 37, 65, and 105 fractions promote butyrate production and stimulate the growth of butyrate-producing bacteria in the human gut, thereby conferring beneficial effects on gut health.

Peptide-based pore formation and cell membrane deformation: European Biophysics Journal Prizes at EBSA 2023.

The European Biophysics Journal Prizes awarded at the European Biophysical Societies Association (EBSA) Congress in Stockholm in the Summer of 2023 recognised papers published in 2020 and 2021 which made use of multiple complementing experimental, theoretical and computational approaches. One of the winning papers addressed the specific role of arginine residues within antimicrobial and cell-penetrating peptides, in promoting membrane defect stabilisation and pore formation. The other winning paper described the influence of atomic force microscopy probe geometry on the measurement of surface deformability, assessed for investigation of the differing viscoelastic properties of non-malignant and cancerous cells. These papers showcase biophysical science; the importance of combining different experimental, modelling and molecular dynamics methods; and how researchers need to understand the theoretical basis and the limitations of the techniques they use. EBSA warmly congratulates the authors on their work and its subsequent recognition. Publication of these papers also demonstrates the ongoing commitment of the European Biophysics Journal to molecular scale and to systems biophysics, and to support of the international biophysical community.

Adverse childhood experiences and stress among oral health students: a descriptive correlational study.

Background: Stress is a challenge to many post-secondary students and, if prolonged and unmanaged, can affect academic success. Understanding factors that contribute to students' stress is important. One possible contributor may be adverse childhood experiences (ACEs); that is, traumatic events that occur during the first 18 years of life. Inverse relationships between the number of ACEs and indicators of poor mental well-being have been proposed. Objective: To describe ACEs in oral health students (OHS) and the associations between the number and types of ACEs and levels of perceived stress, an indicator of mental well-being. Methods: Invitations to participate in an anonymous online cross-sectional survey were sent to all OHS, 19 years and older, attending Dalhousie University in Halifax, Nova Scotia, Canada. Self-reports of ACEs and perceived stress were collected. Zero-order correlations and regression modelling were used to examine associations. Results: Twenty-six percent (26%, n = 66) of OHS completed the survey. Respondents reported an average of 2.20 ACEs; 34.9% reported ≥ 3 ACEs. Emotional abuse (41%) was the most reported ACE. Associations were observed between numbers of ACEs and stress. Levels of stress increased with the number of ACEs (r = 0.23, p < 0.05). Regression modelling determined levels of stress were not affected by ACE type (F (3,62) = 2.24, p = 0.092). Discussion: This was the first study to examine associations between ACEs and perceived stress in OHS. These students reported greater numbers of ACEs than age-matched general populations. Levels of stress were associated with numbers of ACEs. Conclusion: Faculty in dental and dental hygiene programs should recognize the prevalence of ACEs among OHS and the potential impact on their mental well-being.

Contexte: Le stress est un défi pour de nombreux étudiants du postsecondaire : s'il est ressenti sur une longue période et s'il n'est pas géré, il peut nuire à la réussite scolaire. Il est important de comprendre les facteurs qui contribuent au stress des étudiants. Les expériences négatives durant l'enfance (ENE), c.-à-d. les événements traumatiques vécus au cours des 18 premières années de vie, peuvent constituer l'un de ces facteurs. On a suggéré une corrélation inverse entre le nombre d'ENE et les indicateurs d'un mauvais bien-être mental. Objectif: Décrire les ENE chez les étudiants en santé buccodentaire (ESB) et les corrélations entre les types et le nombre d'ENE d'une part et les niveaux de stress perçus, un indicateur du bien-être mental, d'autre part. Méthodes: On a fait parvenir des invitations à participer à un sondage transversal anonyme en ligne à tous les ESB âgés de 19 ans et plus qui fréquentent l'Université Dalhousie à Halifax, en Nouvelle-Écosse (Canada). On a recueilli des données autodéclarées sur les ENE et le stress perçu. Des corrélations d'ordre zéro et la modélisation par régression ont été utilisées pour examiner les relations entre les données. Résultats: Vingt-six pour cent (26 %, n = 66) des ESB ont répondu au sondage. En moyenne, les répondants ont fait mention de 2,20 ENE, et 34,9 % ont déclaré ≥ 3 ENE. La violence psychologique (41 %) était le type d'ENE le plus largement déclaré. On a constaté des corrélations entre le nombre d'ENE et le niveau de stress. Les niveaux de stress augmentaient avec le nombre d'ENE (r = 0,23, p < 0,05). La modélisation par régression a permis d'établir que les types d'ENE n'avaient pas d'incidence sur les niveaux de stress (F [3,62] = 2,24, p = 0,092). Discussion: Il s'agissait de la première étude à examiner les relations entre les ENE et le stress perçu par les ESB. Ces étudiants ont déclaré un plus grand nombre d'ENE que la même classe d'âge dans la population générale. On a constaté une corrélation entre les niveaux de stress et le nombre d'ENE. Conclusion: Les membres du corps professoral des programmes dentaires et d'hygiène dentaire doivent reconnaître la prévalence des ENE parmi les ESB ainsi que les effets éventuels sur leur bien-être mental.

Special Issue: 18th Congress of the Polish Biophysical Society.

The 18th Congress of the Polish Biophysical Society took place at the Faculty of Physics of the University of Warsaw in Warsaw, Poland, in September 2022. In total, 111 attendees (Attendance Profile: 107 in-person, 4 remote; Italy 1, Lithuania 1, Poland 104, United Kingdom 1, United States 4) participated in the event. The authors of lectures and posters at the Congress were invited to prepare their presentations in the form of articles in this special issue of the European Biophysics Journal. The 11 articles published in this special issue present a limited sampling of the subjects of the conference presentations. Nevertheless, they showcase excellence in Polish biophysics across a wide range of topics, using both theoretical and experimental approaches: mechanisms of receptor-ligand interactions, medical applications of proteins and nucleic acids, non-linear dynamics/molecular dynamics of protein systems, hydrodynamics and biosensing. We hope to improve on the representation of the international Polish biophysical community after the next Congress in 2025.

Development of a model for granule-bound starch synthase I activity using free-energy calculations.

Starch is a branched polymer of glucose with two components, both of which have (1 â†’ 4)-α linear links and (1 â†’ 6)-α branch points: amylopectin, of high molecular weight with many short branches, and amylose, of lower molecular weight and only a few long-chain branches. Granule-bound starch synthase I (GBSSI) is one of the main enzymes controlling amylose synthesis and chain-length distribution. As production of different GBSSI mutants is time-consuming and laborious, molecular dynamics (MD) simulations are used here to predict the binding of different GBSSI mutants to a representative amylose fragment. The simulations were atomistic, with explicit solvent and docking, a method successfully used to understand the binding of wild-type GBSSI to amylose fragments. The binding of GBSSI to G5 (a pentasaccharide amylose fragment) is combined with free-energy calculations employing a thermodynamic integration method to predict the effects of mutations on enzyme activity. Ten GBSSI mutants with different enzyme activities were analyzed to find the structural and energy changes among different single amino-acid mutants and their possible relationship to starch characteristics. Comparing the structural changes and the relative binding free energy of G5 to the wild type GBSSI and GBSSI mutants, it was found that mutants with negative binding energy (lower than -2.0 kcal/mol) are more likely to have higher enzyme activity and amylose content compared to the wild type. This theoretical paper used simulations and robust free energy calculations to interpret in planta data with potential predictions as to what mutants might be generated to give desired properties. This study can be used to help develop grains with improved functional properties.

The adherence to the American Association for the Study of Liver Diseases 2018 guidelines in the management of hepatocellular carcinoma and its impact on survival.

Introduction: In two Korean and Italian studies, the adherence rate (AR) to ASSLD 2005 guidelines in the management of hepatocellular carcinoma (HCC) was 60%. In a US study, the AR to American Association for the Study of Liver Disease (AASLD) 2005 guidelines was 73.3%, 26.8%, 25.3%, and 58.8% for patients with Barcelona Clinic Liver Cancer (BCLC) Stage A, B, C, and D, respectively, and nonadherence to guidelines was associated with longer overall survival (OS) in patients with BCLC Stage D. Here, we explored the AR to AASLD 2018 guidelines and its impact on OS. Methods: Between 2017 and 2019, 148 unique treatment-naïve patients with HCC were identified. Patients were staged according to the BCLC staging system and their AR to AASLD 2018 guidelines was noted. OS was estimated using Kaplan-Meier method. Survivals among patients from different groups was compared using Log-rank test. Results: The overall AR to AASLD 2018 guidelines was 83%. The AR for BCLC Stages 0, A, B, C, and D were 100%, 97%, 77%, 77%, and 38%, respectively. In patients with BCLC Stage D, the OS of patients treated with modalities adherent versus nonadherent to AASLD 2018 guidelines was 0.03 vs. 5.2 months (P = 0.0005). Otherwise, adherence versus nonadherence to AASLD 2018 guidelines showed no statistically significant differences in OS for patients with BCLC Stages 0, A, B, and C. Conclusion: The overall AR to AASLD 2018 guidelines was 83%. Nonadherence to AASLD 2018 guidelines in patients with BCLC Stage D translated into better OS.

Surface plasmon resonance and microscale thermophoresis approaches for determining the affinity of perforin for calcium ions.

Perforin is a pore-forming protein that plays a crucial role in the immune system by clearing virus-infected or tumor cells. It is released from cytotoxic granules of immune cells and forms pores in targeted lipid membranes to deliver apoptosis-inducing granzymes. It is a very cytotoxic protein and is therefore adapted not to act in producing cells. Its activity is regulated by the requirement for calcium ions for optimal activity. However, the exact affinity of perforin for calcium ions has not yet been determined. We conducted a molecular dynamics simulation in the absence or presence of calcium ions that showed that binding of at least three calcium ions is required for stable perforin binding to the lipid membrane. Biophysical studies using surface plasmon resonance and microscale thermophoresis were then performed to estimate the binding affinities of native human and recombinant mouse perforin for calcium ions. Both approaches showed that mouse perforin has a several fold higher affinity for calcium ions than that of human perforin. This was attributed to a particular residue, tryptophan at position 488 in mouse perforin, which is replaced by arginine in human perforin. This represents an additional mechanism to control the activity of human perforin.

Proceedings of the 25th Analytical Ultracentrifugation Workshops and Symposium.

The 25th International Analytical Ultracentrifugation (AUC) Workshops and Symposium (AUC2022) took place at the University of Lethbridge in Lethbridge, Canada, in July 2022. In total, 104 attendees (Attendance Profile: 104 attendees, 69 in-person, 35 remote. Brazil 1, Canada 24, China 1, Czech Republic 2, Finland 1, France 3, Germany 22, India 3, Italy 1, Japan 4, Spain 1, Switzerland 3, Taiwan 1, United Kingdom 5, United States 32) participated in the event and presented the latest advances in the field. While the primary focus of the conference was to showcase the applications of AUC in chemical, life sciences, and nanoparticle disciplines, several presentations also integrated complementary methods, such as isothermal titration calorimetry, microscale thermophoresis, light scattering (static and dynamic), small-angle X-ray scattering, X-ray crystallography, and cryo-electron microscopy. Additionally, the delegates gained valuable hands-on experience from 20 workshops covering a broad range of applications, experimental designs and systems, and the latest software innovations in solution biophysics. The AUC2022 special volume highlights the sustained innovation, utility and relevance of AUC and related solution biophysical methods across various disciplines, including biochemistry, structural biology, synthetic polymer chemistry, carbohydrate chemistry, protein and nucleic acid characterization, nano-science, and macromolecular interactions.

Critical examination of the characterization techniques, and the evidence, for the existence of extra-long amylopectin chains.

It has been suggested that amylopectin can contain small but significant amounts of extra-long chains (ELCs), which could affect functional properties, and also would have implications for the mechanism of starch biosynthesis. However, current evidence for the existence of ELCs is ambiguous. The amylose/amylopectin separation and the characterization techniques used for the investigation of ELCs are reviewed, problems in those techniques are examined, and studies of ELCs of amylopectin are discussed. A model for the biosynthesis of amylopectin chains in terms of conventional biosynthesis enzymes, which provides an excellent fit to a large amount of experimental data, is used to provide a rigorous definition of ELCs. In addition, current investigations of ELCs, involving separation, is hindered by the lack of a method to quantitatively separate all the amylopectin from starch without any traces of residual amylose (which would have long chains). Unambiguous evidence for the existence of ELCs can be obtained using two-dimensional (2D) characterization, these dimensions being the degree of polymerization of a chain and the size of the whole molecule. Available 2D data indicate that there are no ELCs present in currently detectable quantities in native rice starches. However, concluding this more rigorously requires improvements in the resolution of current 2D methods.

Effects of the Molecular Structure of Starch in Foods on Human Health.

Starch provides approximately half of humans' food energy, and its structural features influence human health. The most important structural feature is the chain length distribution (CLD), which affects properties such as the digestibility of starch-containing foods. The rate of digestion of such foods has a strong correlation with the prevalence and treatment of diseases such as diabetes, cardiovascular disease and obesity. Starch CLDs can be divided into multiple regions of degrees of polymerization, wherein the CLD in a given region is predominantly, but not exclusively, formed by a particular set of starch biosynthesis enzymes: starch synthases, starch branching enzymes and debranching enzymes. Biosynthesis-based models have been developed relating the ratios of the various enzyme activities in each set to the CLD component produced by that set. Fitting the observed CLDs to these models yields a small number of biosynthesis-related parameters, which, taken together, describe the entire CLD. This review highlights how CLDs can be measured and how the model-based parameters obtained from fitting these distributions are related to the properties of starch-based foods significant for health, and it considers how this knowledge could be used to develop plant varieties to provide foods with improved properties.