Mechanical regulation of talin through binding and history-dependent unfolding.

Talin is a force-sensing multidomain protein and a major player in cellular mechanotransduction. Here, we use single-molecule magnetic tweezers to investigate the mechanical response of the R8 rod domain of talin. We find that under various force cycles, the R8 domain of talin can display a memory-dependent behavior: At the same low force (<10 pN), the same protein molecule shows vastly different unfolding kinetics. This history-dependent behavior indicates the evolution of a unique force-induced native state. We measure through mechanical unfolding that talin R8 domain binds one of its ligands, DLC1, with much higher affinity than previously reported. This strong interaction can explain the antitumor response of DLC1 by regulating inside-out activation of integrins. Together, our results paint a complex picture for the mechanical unfolding of talin in the physiological range and a new mechanism of function of DLC1 to regulate inside-out activation of integrins.

Nonexponential kinetics captured in sequential unfolding of polyproteins over a range of loads.

While performing under mechanical loads in vivo, polyproteins are vitally involved in cellular mechanisms such as regulation of tissue elasticity and mechano-transduction by unfolding their comprising domains and extending them. It is widely thought that the process of sequential unfolding of polyproteins follows an exponential kinetics as the individual unfolding events exhibit identical and identically distributed (iid) Poisson behavior. However, it was shown that under high loads, the sequential unfolding kinetics displays nonexponential kinetics that alludes to aging by a subdiffusion process. Statistical order analysis of this kinetics indicated that the individual unfolding events are not iid, and cannot be defined as a Poisson (memoryless) process. Based on numerical simulations it was argued that this behavior becomes less pronounced with lowering the load, therefore it is to be expected that polyproteins unfolding under lower forces will follow a Poisson behavior. This expectation serves as the motivation of the current study, in which we investigate the effect of force lowering on the unfolding kinetics of Poly-L8 under varying loads, specifically high (150, 100 â€‹pN) and moderate-low (45, 30, 20 â€‹pN) forces. We found that a hierarchy among the unfolding events still exists even under low loads, again resulting in nonexponential behavior. We observe that analyzing the dwell-time distributions with stretched-exponentials and power laws give rise to different phenomenological trends. Using statistical order analysis, we demonstrated that even under the lowest load, the sequential unfolding cannot be considered as iid, in accord with the power law distribution. Additional free energy analysis revealed the contribution of the unfolded segments elasticity that scales with the force on the overall one-dimensional contour of the energy landscape, but more importantly, it discloses the hierarchy within the activation barriers during sequential unfolding that account for the observed nonexponentiality.

Kinetic Method of Producing Pores Inside Protein-Based Biomaterials without Compromising Their Structural Integrity.

Hydrogels made from globular proteins cross-linked covalently into a stable network are becoming an important type of biomaterial, with applications in artificial tissue design and cell culture scaffolds, and represent a promising system to study the mechanical and biochemical unfolding of proteins in crowded environments. Due to the small size of the globular protein domains, typically 2-5 nm, the primary network allows for a limited transfer of protein molecules and prevents the passing of particles and aggregates with dimensions over 100 nm. Here, we demonstrate a method to produce protein materials with micrometer-sized pores and increased permeability. Our approach relies on forming two competing networks: a covalent network made from cross-linked bovine serum albumin (BSA) proteins via a light-activated reaction and a physical network triggered by the aggregation of a polysaccharide, alginate, in the presence of Ca2+ ions. By fine-tuning the reaction times, we produce porous-protein hydrogels that retain the mechanical characteristics of their less-porous counterparts. We further describe a simple model to investigate the kinetic balance between the nucleation of alginate and cross-linking of BSA molecules and find the upper rate of the alginate aggregation reaction driving pore formation. By enabling a more significant permeability for protein-based materials without compromising their mechanical response, our method opens new vistas into studying protein-protein interactions and cell growth and designing novel affinity methods.

Quality of Life and Nutritional Status of the Geriatric Population of the South-Central Part of Nepal.

BACKGROUND: The main objective of the study was to assess the nutritional status and quality of life in the geriatric population of Lahan municipality of Siraha district. METHODS: A cross-sectional analytical study was conducted in Lahan municipality of Siraha district from June to December 2017. The Mini-Nutritional Assessment tool was used to investigate the nutritional status, and World Health Organization Quality of Life-OLD questionnaires were used to assess the quality of life among geriatric population. RESULT: Out of the total participants, one-third (45.7%) of the participants were at risk of malnutrition and 19.8% were malnourished while 34.5% had normal nutritional status. It was seen that 48.2% of participants had good quality of life whereas 51.8% of them had poor quality of life. There was a significant association between nutritional status and quality of life in the elderly population. CONCLUSION: The findings showed the need for active ageing interventions to improve the nutritional status and quality of life of elders at the community settings. Proper attention should be focused on elders' nutrition to reduce the observed prevalence of malnutrition, and focus should be given on the nutrition status that leads to improve the quality of life of elders.

Pregnancy Induced Hypertension among Pregnant Women Delivering in a Tertiary Care Hospital: A Descriptive Cross-sectional Study.

INTRODUCTION: Pregnancy Induced Hypertension is a major health issue with limited studies conducted so far in Chitwan, Nepal regarding adverse perinatal outcomes in obstetric population. This study aimed to find prevalence of pregnancy induced hypertension among pregnant women delivering in a tertiary care hospital. METHODS: A descriptive cross-sectional study was conducted in a teaching hospital of Chitwan, Nepal during the study period of six months from 15th Jan 2019- 16th July 2019 after getting ethical approval from Chitwan Medical College-Institutional Review Committee (Reference number-2075/076042). Women were selected via convenience sampling technique. Face to face interview was conducted to collect socio-demographic and obstetric data whereas, data related to the fetomaternal outcomes were obtained from patient charts and delivery record books. Statistical Package for Social Sciences version 20 was used for data analysis. Point estimate at 95% confidence interval was calculated along with frequency and proportion for binary data. RESULTS: The prevalence of pregnancy induced hypertension was found to be 91 (6.43%) (3.83-9.03 at 95% Confidence Interval) representing 71 (78.1%), 12 (13.2%), and 8 (8.7%) as gestational hypertension, preeclampsia and eclampsia respectively. CONCLUSIONS: The burden of pregnancy induced hypertension was found quite higher as compared to other similar studies done in Nepal. Gestational hypertension was most common type.

Does protein unfolding play a functional role in vivo?

Unfolding and refolding of multidomain proteins under force have yet to be recognized as a major mechanism of function for proteins in vivo. In this review, we discuss the inherent properties of multidomain proteins under a force vector from a structural and functional perspective. We then characterize three main systems where multidomain proteins could play major roles through mechanical unfolding: muscular contraction, cellular mechanotransduction, and bacterial adhesion. We analyze how key multidomain proteins for each system can produce a gain-of-function from the perspective of a fine-tuned quantized response, a molecular battery, delivery of mechanical work through refolding, elasticity tuning, protection and exposure of cryptic sites, and binding-induced mechanical changes. Understanding how mechanical unfolding and refolding affect function will have important implications in designing mechano-active drugs against conditions such as muscular dystrophy, cancer, or novel antibiotics.