Conservative versus Surgical Treatment of Pneumatosis Intestinalis: Experience from a Multidisciplinary Center.

BACKGROUND Pneumatosis intestinalis (PI) is an uncommon condition that is not specific to any particular disease. Currently, there is no specific clinical guideline for treating and diagnosing PI. Furthermore, there are numerous causes of PI, which makes it difficult for clinicians - internal medicine physicians as well as surgeons - to take a clinical approach to diagnosis and treatment. CASE REPORT We present 3 clinical scenarios with PI. In the first patient there was a solitary image of PI, which was treated successfully with parenteral nutrition and intravenous antibiotics, and he was discharged after 5 days. The other 2 cases, which involve gas in the hepatic portal vein (HPVG), were handled in 2 distinct ways: surgically and conservatively. One needed diagnostic laparoscopy with necrotic segmentectomy and was discharged from the hospital on postoperative day 16. The last patient, received resuscitation treatment due to severe comorbidities and inability to tolerate surgery. After 3 days, abdominal CT scan revealed no signs of remaining PI. However, the patient was terminally discharged after 7 weeks of treatment due to septic shock caused by sacrococcygeal ulcer and urinary tract infection. By drawing comparisons among these 3 scenarios, we aim to highlight certain indicators for conservative treatment success. CONCLUSIONS PI with HPVG is a sign of severe prognosis, which often requires surgical intervention. However, the decision to manage conservatively or surgically depends on the patient's condition and other criteria such as peritonitis, free fluid in the abdominal cavity, and the presence of shock. Physicians should also weigh the benefits and risks of surgical intervention in critically ill patients.

Indoor air pollution is associated with respiratory symptoms in children in urban Vietnam.

Exposure to indoor air pollution (IAP) is a leading environmental risk for respiratory diseases. We investigated the relationship between respiratory symptoms and polluting indoor activities such as smoking, cooking and contact with pets among children in Ho Chi Minh City (HCMC), Vietnam. A cross-sectional survey applied a multistage sampling method in 24 randomly selected secondary schools across the city. Approximately 15,000 students completed self-administrated questionnaires on risk factors and respiratory health outcomes within the preceding 12 months. Data were analyzed using a multivariable logistic regression model with robust standard errors. Wheeze was the most common respiratory symptom (39.5 %) reported, followed by sneezing and runny nose (28.3 %). A small percentage of students self-reported asthma (8.6 %). Approximately 56 % of participants lived with family members who smoked. A positive association between exposure to indoor secondhand smoke and respiratory symptoms was observed, with adjusted odds ratios (aOR) of 1.41 (95 % CI: 1.25-1.60, p < 0.001) for wheezing and 1.64 (95 % CI: 1.43-1.87, p < 0.001) for sneezing and runny nose, respectively. Using an open stove fuelled by coal, wood, or kerosene for cooking was associated with wheeze (aOR: 1.36, CI 95 %: 1.10-1.68, p = 0.01) and sneezing and runny nose (aOR: 1.36, CI 95 %: 1.09-1.69, p = 0.01). In the present study, IAP was associated with adverse health outcomes, as evidenced by an increase in respiratory symptoms reported within the previous 12 months.

Environmental behaviors and toxic mechanisms of engineered nanomaterials in soil.

Engineered nanomaterials (ENMs) are inevitably released into the environment with the exponential application of nanotechnology. Parts of ENMs eventually accumulate in the soil environment leading to potential adverse effects on soil ecology, crop production, and human health. Therefore, the safety application of ENMs on soil has been widely discussed in recent years. More detailed safety information and potential soil environmental risks are urgently needed. However, most of the studies on the environmental effects of metal-based ENMs have been limited to single-species experiments, ecosystem processes, or abiotic processes. The present review formulated the source and the behaviors of the ENMs in soil, and the potential effects of single and co-exposure ENMs on soil microorganisms, soil fauna, and plants were introduced. The toxicity mechanism of ENMs to soil organisms was also reviewed including oxidative stress, the release of toxic metal ions, and physical contact. Soil properties affect the transport, transformation, and toxicity of ENMs. Toxic mechanisms of ENMs include oxidative stress, ion release, and physical contact. Joint toxic effects occur through adsorption, photodegradation, and loading. Besides, future research should focus on the toxic effects of ENMs at the food chain levels, the effects of ENMs on plant whole-lifecycle, and the co-exposure and long-term toxicity effects. A fast and accurate toxicity evaluation system and model method are urgently needed to solve the current difficulties. It is of great significance for the sustainable development of ENMs to provide the theoretical basis for the ecological risk assessment and environmental management of ENMs.

Association between Asbestos Exposure and the Incidence of Kidney Cancer: a Weight-of-Evidence Evaluation and Meta-analysis.

PURPOSE OF REVIEW: Occupational asbestos exposure has been extensively linked to various cancers, with ongoing debates regarding its association with kidney cancer. This study aims to investigate the correlation between occupational asbestos exposure and kidney cancer incidence. Additionally, potential influencing factors are analyzed to enhance the comprehension of the relationship between asbestos exposure and kidney cancer. RECENT FINDING: While asbestos has established strong associations with malignant mesothelioma and lung cancer, its connection to other malignancies such as gastric, colorectal, and kidney cancers remains under scrutiny. The current study presents mixed opinions on the relationship between asbestos exposure and kidney cancer. Our analysis revealed a potential association between asbestos exposure and the incidence of kidney cancer. Notably, among different types of asbestos, exposure to amphibole appeared to be particularly linked to a higher incident risk of kidney cancer.

Fundamental Determinants of the Accuracy of Equilibrium Constants for Affinity Complexes.

The equilibrium constant of a chemical reaction is arguably the key thermodynamic parameter in chemistry; we naturally expect that equilibrium constants are determined accurately. The majority of equilibrium constants determined today are those of binding reactions that form affinity complexes, such as protein-protein, protein-DNA, and protein-small molecule. There is growing awareness that the determination of equilibrium constants for highly stable affinity complexes may be very inaccurate. However, fundamental (i.e., method-independent) determinants of accuracy are poorly understood. Here, we present a study that explicitly shows what the accuracy of equilibrium constants of affinity complexes depends on. This study reveals the critical importance of the choice of concentration of interacting components and creates a theoretical foundation for improving the accuracy of the equilibrium constants. The predicted influence of concentrations on accuracy was confirmed experimentally. The results of this fundamental study provide instructive guidance for experimentalists independently on the method they use.

Learning to reason over scene graphs: a case study of finetuning GPT-2 into a robot language model for grounded task planning.

Long-horizon task planning is essential for the development of intelligent assistive and service robots. In this work, we investigate the applicability of a smaller class of large language models (LLMs), specifically GPT-2, in robotic task planning by learning to decompose tasks into subgoal specifications for a planner to execute sequentially. Our method grounds the input of the LLM on the domain that is represented as a scene graph, enabling it to translate human requests into executable robot plans, thereby learning to reason over long-horizon tasks, as encountered in the ALFRED benchmark. We compare our approach with classical planning and baseline methods to examine the applicability and generalizability of LLM-based planners. Our findings suggest that the knowledge stored in an LLM can be effectively grounded to perform long-horizon task planning, demonstrating the promising potential for the future application of neuro-symbolic planning methods in robotics.

Wearing masks as a protective measure for children against traffic-related air pollution: A comparison of perceptions between school children and their caregivers in Ho Chi Minh City, Vietnam.

BACKGROUND: Traffic-related air pollution (TRAP) problems are unlikely to be solved in the short term, making it imperative to educate children on protective measures to mitigate the negative impact on their health. Children and their caregivers may hold differing views on wearing a face mask as a safeguard against air pollution. While many studies have focused on predicting children's health-protective behaviours against air pollution, few have explored the differences in perceptions between children and their caregivers. OBJECTIVES: To examine this, we conducted a study that compared the health beliefs of two generations and evaluated the factors that influence the use of masks by children to reduce air pollution exposure. METHODS: The study was conducted in 24 secondary schools and involved 8420 children aged 13-14 and their caregivers. We used a Health Belief Model (HBM)-based instrument containing 17-item self-administered health beliefs questionnaires to gather data. The results were analysed using hierarchical logistic regression to determine the probability of children frequently wearing masks to protect against TRAP. RESULTS: Our study showed both children and caregivers recognised that several factors could influence mask-wearing among children: discomfort or difficulty breathing while wearing a mask and forgetting to bring a mask when going outside; perceived threats of the poor quality of air and children's respiratory health problems; and cues to mask use (i.e., seeing most of their friends wearing facemasks and ease of finding masks in local stores). However, only children were significantly concerned with public perception of their appearance while wearing a mask. Females were more likely to wear masks, and caregivers with higher levels of education were more likely to encourage their children to wear masks. Children who commuted to schools by walking, biking, or motorbiking were also more accepting of mask-wearing than those who travelled by car or bus. CONCLUSIONS: Children and their caregivers hold different perceptions of wearing masks to protect against air pollution. Children are more susceptible to social judgements regarding their appearance when wearing a mask.

Quality of Life of Patients With Chronic Venous Insufficiency of the Lower Extremities Before and After Endovascular Laser Ablation: A Prospective Pilot Study Using the Chronic Venous Insufficiency Quality of Life Questionnaire 20 (CIVIQ-20).

Background Chronic venous insufficiency of the lower extremities is a condition in which blood stagnates in the venous system, causing symptoms of pain, fatigue, leg edema, and cramps. Although this disease progresses slowly and is not fatal, its symptoms lead to a decline in quality of life, affecting the patient's work. One of the current surgical treatment methods for patients with indications for surgical removal of the saphenous vein is endovenous laser ablation (EVLA). After EVLA, besides evaluating the effectiveness of surgery, and the rate of complications, one of the aspects that need attention is improving quality of life. The objective of this study was to assess the quality of life of patients with chronic venous insufficiency of the lower extremities before and after endovascular laser intervention, analyzing changes in ChronIc Venous Insufficiency Quality of Life Questionnaire 20 (CIVIQ-20) scores in each domain of quality of life. Methodology A total of 41 patients with chronic venous insufficiency of the lower extremities were enrolled in this study, who were classified as C2 to C6 and were treated by endovenous laser ablation. QoL was measured by using the ChronIc Venous Insufficiency Quality of Life Questionnaire 20 (CIVIQ-20) questionnaire pre- and post-operatively. Pain scores and clinical severity were also evaluated using the visual analog scale (VAS) and the venous clinical severity score (VCSS) one month after EVLA. Results The mean age was 52.17 ± 11.23 years. The mean duration of symptoms was 7.29 ± 3.58 years, the median laser ablation time was 40 minutes, and the mean time to return to normal activities was 5.7 ± 1.8 days. The CIVIQ-20 score at baseline was 47.8 ± 7.4 and 31.1 ± 3.9 after one-month laser ablation. The quality of life has significantly improved after intervention using laser treatment (p < 0.001). The VAS and VCSS scores after laser treatment were lower than the baseline (p < 0.001). In our study, there was a statistically significant correlation between the change of CIVIQ-20 and the change of VCSS (r = 0.63, p < 0.001). Conclusion CIVIQ-20 is a reliable toolkit to assess the quality of life of patients with chronic venous insufficiency of the lower extremities. The patient's quality of life improved markedly after the intervention.

Classification of COPD as ABCD according to GOLD 2011 and 2017 versions in COPD patients at University Medical Center in Ho Chi Minh City, Vietnam.

In 2017, Global Initiative for Chronic Lung Disease (GOLD) made substantial changes to its ABCD group categorization. Although several studies had been conducted to assess the impact of the new GOLD category, there was no research on the change of the GOLD classification in Vietnam. This retrospective analysis was conducted at Asthma and COPD clinic at the University Medical Center in Ho Chi Minh City, Vietnam. Our study population comprised patients visiting Medical Center from January 2018 to January 2020. We categorized patients' demographic, clinical characteristics and pharmacotherapy based on GOLD 2011 and 2017 guidelines. A comparison between the two versions was also determined. A total of 457 patients were included in this study. The percentage of groups A, B, C and D according to GOLD 2011 was 5%, 20.8%, 13.1% and 61.1%; and according to GOLD 2017 was 6.1%, 34.1%, 12% and 47.8%, respectively. In terms of gender, male patients constituted nearly 95% of the study's population (433/457 patients). Regarding pharmacotherapy, approximately 20% of the low-risk group (group A-B) was overtreated with ICS components: LABA+ICS (15.8%) and LAMA+LABA+ICS (3.8%). There were 13.3% and 1.1% of patients transferred from D to B and from C to A, respectively. All of them had lower FVC% pred, FEV1% pred and FEV1/FVC than the patients remained in group B or A (p<0.005). This is the first research in Vietnam to show the distribution of COPD patients using both the GOLD 2011 and GOLD 2017 criteria. There was 14% of patients reclassified from high-risk groups to low-risk groups when changing from 2011 to 2017 version and discordance of medications between guidelines and real-life practice. Therefore, clinicians should use their clinical competence to consider patients' conditions before deciding the appropriate therapeutic approach. Consequently, further studies were required to evaluate the effect of the change in GOLD classification.

Ru-Catalyzed Asymmetric Reductive Amination of Aryl-Trifluoromethyl Ketones for Synthesis of Primary α-(Trifluoromethyl)arylmethylamines.

The ruthenium-catalyzed asymmetric reductive amination of aryl-trifluoromethyl ketones affording high value primary α-(trifluoromethyl)arylmethylamines using cheap NH4OAc as the nitrogen source and H2 as the reductant is reported. This user-friendly and simple catalytic method tolerates various aromatic functions with electron-withdrawing or -donating substituents at the para- or meta-positions and as well challenging heteroaromatic functions, yielding primary α-(trifluoromethyl)arylmethylamines with excellent chemoselectivities, enantioselectivities, and useful yields (80-97% ee, 51-92% isolated yields). Finally, scalable and concise synthesis of key drug intermediates using this methodology is presented.

The High Re-Ulceration Rate in Lower Extremity Amputation Intervention in Type 2 Diabetic Vietnamese Patients After 24-Month Follow-Up at Cho Ray Hospital, Vietnam.

Diabetic foot ulcers (DFU) are a prevalent and severe disease with vascular and/or neurological complications, and if not diagnosed and treated promptly, it may rapidly deteriorate. Despite amputation or nonamputation treatment, there is still a high rate of re-ulceration. Previous studies have shown that the recurrence rate varies from 43% to 59% after 2 years. Currently, there is still a high rate of lower extremity amputation intervention, particularly above-the-ankle amputation, at Cho Ray Hospital in Vietnam, reaching 50%. The effectiveness of this intervention in the long term based on re-ulceration has not been evaluated in Vietnamese diabetic patients (DPs). This study aims to describe the long-term outcomes of amputation intervention in Type 2 DPs after 24 months and identify factors related to DFU recurrence in order to improve DFU management in low-middle-income countries like Vietnam. From January to June 2022, archived clinical and direct visit or phone follow-up data were collected and analyzed from diabetic foot ulcer patients with low extremity amputation who were treated at Cho Ray hospital from 2018 to 2020. The high re-ulceration rate in the 24th month was 29.8% (17/57), and the factor related to this outcome was "late diagnosis and care" (32.4 days vs 26.9 days with P = .03). Other potential factors (higher rates but no significant statistical difference with P > .05) included failure of HbA1c control greater than 9% (82.5% vs 67.5%), the severity of foot ulcers with TEXAS 3B (82% vs 60%), the number of years having diabetes (8.7 years vs 6.7 years), loss of monofilament sensation (82.5% vs 70.6%), and a history of diabetic foot ulcer (17.6% vs 10%). The re-ulceration after 24 months might depend on various clinical factors. Therefore, early diagnosis and care for diabetic foot ulcers could help reduce amputation rates and the risk of re-ulceration.

Pendant Group Modifications Provide Graft Copolymer Silicones with Exceptionally Broad Thermomechanical Properties.

Graft copolymers offer a versatile platform for the design of self-assembling materials; however, simple strategies for precisely and independently controlling the thermomechanical and morphological properties of graft copolymers remain elusive. Here, using a library of 92 polynorbornene-graft-polydimethylsiloxane (PDMS) copolymers, we discover a versatile backbone-pendant sequence-control strategy that addresses this challenge. Small structural variations of pendant groups, e.g., cyclohexyl versus n-hexyl, of small-molecule comonomers have dramatic impacts on order-to-disorder transitions, glass transitions, mechanical properties, and morphologies of statistical and block silicone-based graft copolymers, providing an exceptionally broad palette of designable materials properties. For example, statistical graft copolymers with high PDMS volume fractions yielded unbridged body-centered cubic morphologies that behaved as soft plastic crystals. By contrast, lamellae-forming graft copolymers provided robust, yet reprocessable silicone thermoplastics (TPs) with transition temperatures spanning over 160 °C and elastic moduli as high as 150 MPa despite being both unentangled and un-cross-linked. Altogether, this study reveals a new pendant-group-mediated self-assembly strategy that simplifies graft copolymer synthesis and enables access to a diverse family of silicone-based materials, setting the stage for the broader development of self-assembling materials with tailored performance specifications.

Burden of asthma-like symptoms and a lack of recognition of asthma in Vietnamese children.

OBJECTIVE: Lack of recognition of asthma in childhood results in unmet asthma treatment needs and leads to the risk of sub-optimal respiratory health. The present study assessed the prevalence of asthmatic under-recognition in middle school children in Vietnam. METHODS: We conducted a school-based survey among 15,112 Vietnamese children. Most of them are aged from 13 to 14. Schools and students were recruited using multi-stage sampling. Respiratory symptoms were collected via self-report using a standardized tool from the International Study of Asthma and Allergies in Childhood. Under-recognition of asthma was defined as a presence of at least one asthma-like symptom but a negative response to having ever asthma. Associations were investigated using logistic regression. RESULTS: Prevalence of asthma-like symptoms was 27.3% and prevalence of physician-diagnosed asthma was 8.5%. Over 80% of symptomatic children were not diagnosed with asthma. Under-recognition of asthma was found more in girls (adjusted odds ratio; aOR = 1.75; 95%CI: 1.54 to 1.98). CONCLUSIONS: Asthma is significantly under-recognized in Vietnamese middle-school children. Urgent action is required to improve the recognition of asthma in Vietnam.

Liver Complications in Untreated Treatment-Ineligible versus Treated Treatment-Eligible Patients with Hepatitis B.

BACKGROUND: A substantial number of patients who do not meet treatment criteria for chronic hepatitis B (CHB) later develop adverse outcomes such as cirrhosis and hepatocellular carcinoma (HCC). Our aim was to determine whether current practice guidelines adequately identify CHB patients who will benefit from antiviral therapy. METHODS: We performed a retrospective cohort study comparing the incidence of adverse liver outcomes (cirrhosis and/or HCC) in untreated treatment-ineligible (at baseline and throughout follow-up) versus treated treatment-eligible patients according to standard American Association for the Study of Liver Diseases (AASLD) 2018 guidance (alanine aminotransferase [ALT] >70/50 U/L for men/women plus hepatitis B virus [HBV] DNA >20,000/2,000 IU/mL for HBeAg+/-) and with a sensitivity analyses using a lower threshold (ALT >40 U/L and HBV DNA >2,000 IU/mL). RESULTS: We reviewed records of 5,840 patients from 5 clinics in California and identified 2,987 treatment-naive non-HCC CHB patients. Of those, 271 patients remained untreated treatment-ineligible, 514 patients were treatment-eligible and initiated treatment, with 5-year cumulative adverse liver incidences of 12.5% versus 7.2%, p = 0.074. On multivariable analysis adjusting for age, sex, diabetes, albumin, platelet count, and HBV DNA, compared to treated treatment-eligible patients, untreated treatment-ineligible patients had a significantly higher risk of adverse liver outcomes (adjusted hazard ratio: 2.38, 95% confidence interval 1.03-5.48, p = 0.04) in main analysis by AASLD 2018 criteria but not in sensitivity analysis using the lower treatment threshold (p = 0.09). CONCLUSION: Patients never meeting standard AASLD 2018 criteria for antiviral therapy and never treated had twice the risk of developing cirrhosis and/or HCC when compared to eligible and treated patients.

Prevalence of depressive disorders in a primary care setting in Ho Chi Minh City, Vietnam: A cross-sectional epidemiological study.

OBJECTIVE: This research was conducted to identify the prevalence and associated factors of depressive disorders, as well as evaluate the recognition rate of general practitioners in detecting these mental health issues in primary care. METHOD: Five hundred and twelve participants (55.3% female, mean age = 46.35 years) were assessed by psychiatrists based on the DSM-5 clinical procedures over a two-month survey in a primary care facility in Ho Chi Minh City, Vietnam. RESULTS: There were 15.8% (95% confidence interval [CI] 12.9-19.2) of the population having depressive disorders, with major depressive disorder being the most prevalent subtype at 8% (95% CI 5.9-10.6). General practitioners could detect depressive disorders in 2.5% of all cases (95% CI .5-7.7). Significantly linked with depressive disorders in multivariable analysis were Chinese ethnic or other minority races (adjusted odds ratios [aOR] = 4.10, 95% CI 1.04-16.12), and low economic status (aOR = 5.41, 95% CI 1.29-22.59). CONCLUSIONS: The high prevalence of depressive disorders in outpatients of primary care clinics may raise the awareness of the practitioners about screening and other appropriate actions to tackle the issue.

Hierarchically engineered nanostructures from compositionally anisotropic molecular building blocks.

The inability to synthesize hierarchical structures with independently tailored nanoscale and mesoscale features limits the discovery of next-generation multifunctional materials. Here we present a predictable molecular self-assembly strategy to craft nanostructured materials with a variety of phase-in-phase hierarchical morphologies. The compositionally anisotropic building blocks employed in the assembly process are formed by multicomponent graft block copolymers containing sequence-defined side chains. The judicious design of various structural parameters in the graft block copolymers enables broadly tunable compositions, morphologies and lattice parameters across the nanoscale and mesoscale in the assembled structures. Our strategy introduces advanced design principles for the efficient creation of complex hierarchical structures and provides a facile synthetic platform to access nanomaterials with multiple precisely integrated functionalities.

Bulk Affinity Assays in Aptamer Selection: Challenges, Theory, and Workflow.

Selection of oligonucleotide aptamers involves consecutive rounds of affinity isolation of target-binding oligonucleotides from a random-sequence oligonucleotide library. Every next round produces an aptamer-enriched library with progressively higher fitness for tight binding to the target. The progress of enrichment can only be accurately assessed with bulk affinity assays in which a library is mixed with the target and one of two quantitative parameters, the fraction of the unbound library (R) or the equilibrium dissociation constant (Kd), is determined. These quantitative parameters are used to help researchers make a key decision of either continuing or stopping the selection. Despite the importance of this decision, the suitability of R and Kd for bulk affinity assays has never been studied theoretically, and researchers rely on intuition when choosing between them. Different approaches used for bulk affinity assays expectedly hinder comparative analyses of selections. Our current work has two goals: to give bulk affinity assays a thorough theoretical consideration and to propose a scientifically justified and practical bulk-affinity-assay approach. We postulate a formal criterion of suitability: a quantitative parameter must satisfy the principle of superposition. R satisfies this principle, while Kd does not, suggesting R as a theoretically preferable parameter. Further, we propose a solution for two limitations of R: its dependence on target concentration and narrow dynamic range. Finally, we demonstrate the use of this algorithm in both computer-simulated and experimental aptamer selection. This study sets a cornerstone in the theory of bulk affinity assays, and it provides researchers with a scientifically sound and instructive approach for conducting bulk affinity assays.

Expression and potential role of FOSB in glioma.

Background: FOSB is reported to be an oncogene in a variety of tumors. However, the expression and role of FOSB in glioma remain obscure. In this study, we aimed to explore the expression of FOSB in glioma and its biological role in glioblastoma multiforme (GBM). Methods: Western blot, immunohistochemical staining, and quantitative real-time polymerase chain reaction (RT-qPCR) were used to detect the expression of FOSB in clinical samples. FOSB was knocked down in cells to determine the effects of FOSB on the phenotypic changes of tumors by plate cloning, CCK-8 assay, and Transwell assay. Finally, subcutaneous tumorigenesis in nude mice was used to observe the tumorigenesis of glioma cell lines after the knockdown of the FOSB gene. Results: FOSB expression was higher in glioma compared with normal brain tissue. After the downregulation of FOSB, the expression of cleaved caspase-3 increased. Plate cloning and CCK-8 experiments showed that the proliferation of glioma cell lines decreased. The Transwell assay demonstrated that the glioblastoma cell lines had lower migration ability after the knockdown of FOSB. Finally, the tumor volume of U87 glioma cells in group sh-FOSB was smaller than that in the control group. The TUNEL staining in vitro showed that the apoptosis of sh-FOSB glioma cells increased. Conclusion: FOSB was highly expressed in glioma tissues. The viability of glioma cells decreased, and the ability of glioma cells to proliferate and migrate was reduced when FOSB was downregulated. Hence, FOSB may promote the development and migration of gliomas.

Transient Incomplete Separation of Species with Close Diffusivity to Study the Stability of Affinity Complexes.

Large molecules can be generically separated from small ones, though partially and temporarily, in a pressure-driven flow inside a capillary. This transient incomplete separation has been only applied to species with diffusion coefficients different by at least an order of magnitude. Here, we demonstrate, for the first time, the analytical utility of transient incomplete separation for species with close diffusion coefficients. First, we prove in silico that even a small difference in diffusivity can lead to detectable transient incomplete separation of species. Second, we use computer simulation to prove that such a separation can be used for the reliable determination of equilibrium dissociation constant (Kd) of complexes composed of similar-sized molecules. Finally, we demonstrate experimentally the use of this separation for the accurate determination of Kd value for a protein-aptamer complex. We conclude that "accurate constant via transient incomplete separation" (ACTIS) can serve as a reference method for affinity characterization of protein-aptamer binding in solution.