Native mass spectrometry of membrane protein-lipid interactions in different detergent environments.

Native mass spectrometry (MS) is revealing the role of specific lipids in modulating membrane protein structure and function. Membrane proteins solubilized in detergents are often introduced into the mass spectrometer; however, commonly used detergents for structural studies, such as dodecylmaltoside, tend to generate highly charged ions, leading to protein unfolding, thereby diminishing their utility for characterizing protein-lipid interactions. Thus, there is a critical need to develop approaches to investigate protein-lipid interactions in different detergents. Here, we demonstrate how charge-reducing molecules, such as spermine and trimethylamine-N-oxide, enable characterization of lipid binding to the bacterial water channel (AqpZ) and ammonia channel (AmtB) in complex with regulatory protein GlnK in different detergent environments. We find protein-lipid interactions are not only protein-dependent but can also be influenced by the detergent and type of charge-reducing molecule. AqpZ-lipid interactions are enhanced in LDAO (n-dodecyl-N,N-dimethylamine-N-oxide), whereas the interaction of AmtB-GlnK with lipids is comparable among different detergents. A fluorescent lipid binding assay also shows detergent dependence for AqpZ-lipid interactions, consistent with results from native MS. Taken together, native MS will play a pivotal role in establishing optimal experimental parameters that will be invaluable for various applications, such as drug discovery, as well as biochemical and structural investigations.

Polyamine detergents tailored for native mass spectrometry studies of membrane proteins.

Native mass spectrometry (MS) is a powerful technique for interrogating membrane protein complexes and their interactions with other molecules. A key aspect of the technique is the ability to preserve native-like structures and noncovalent interactions, which can be challenging depending on the choice of detergent. Different strategies have been employed to reduce charge on protein complexes to minimize activation and preserve non-covalent interactions. Here, we report the synthesis of a class of polyamine detergents tailored for native MS studies of membrane proteins. These detergents, a series of spermine covalently attached to various alkyl tails, are exceptional charge-reducing molecules, exhibiting a ten-fold enhanced potency over spermine. Addition of polyamine detergents to proteins solubilized in maltoside detergents results in improved, charge-reduced native mass spectra and reduced dissociation of subunits. Polyamine detergents open new opportunities to investigate membrane proteins in different detergent environments that have thwarted previous native MS studies.

Impact of Medicaid Expansion on Incidence and Mortality from Gastric and Esophageal Cancer.

BACKGROUND AND AIMS: Individuals in Medicaid expanded states have increased access to treatment for medical conditions and other health care resources. Esophageal and gastric cancer are associated with several modifiable risk factors (e.g. smoking, drinking, Helicobacter pylori infection). The impact of Medicaid expansion on these cancers incidence and mortality remains uninvestigated. METHODS: We evaluated the association between Medicaid expansion and gastric and esophageal cancer incidence and mortality in adults aged 25-64. We employed an observational design using a difference-in-differences method with state level data, from 2010 to 2017. Annual, age-adjusted gastric and esophageal cancer incidence and mortality rates, from the CDC Wonder Database, were analyzed. Rates were adjusted for by several socio-demographic factors. RESULTS: Expansion and non-expansion states were similar in percent Hispanic ethnicity and female gender. The non-expansion states had significantly higher proportion of Black race, diabetics, obese persons, smokers, and those living below the federal poverty line. Adjusted analyses demonstrate that expansion states had significantly fewer new cases of gastric cancer: - 1.6 (95% CI 0.2-3.5; P = 0.08) per 1,000,000 persons per year. No significant association was seen between Medicaid expansion and gastric cancer mortality (0.46 [95% CI - 0.08 to 0.17; P = 0.46]) and esophageal cancer incidence (0.8 [95% CI - 0.08 to 0.24; P = 0.33]) and mortality (1.0 [95% CI - 0.06 to 0.26; P = 0.21]) in multivariable analyses. CONCLUSION: States that adopted Medicaid expansion saw a decrease in gastric cancer incidence when compared to states that did not expand Medicaid. Though several factors may influence gastric cancer incidence, this association is important to consider during health policy negotiations.

Step toward Probing the Nonannular Belt of Membrane Proteins.

Integral membrane proteins are embedded in the biological membrane, where they carry out numerous biological processes. Although lipids present in the membrane are crucial for membrane protein function, it remains difficult to characterize many lipid binding events to membrane proteins, such as those that form the annular belt. Here, we use native mass spectrometry along with the charge-reducing properties of trimethylamine N-oxide (TMAO) to characterize a large number of lipid binding events to the bacterial ammonia channel (AmtB). In the absence of TMAO, significant peak overlap between neighboring charge states is observed, resulting in erroneous abundances for different molecular species. With the addition of TMAO, the weighted average charge state (Zavg) was decreased. In addition, the increased spacing between nearby charge states enabled a higher number of lipid binding species to be observed while minimizing mass spectral peak overlap. These conditions helped us to determine the equilibrium binding constants (Kd) for up to 16 lipid binding events. The binding constants for the first few lipid binding events display the highest affinity, whereas the binding constants for higher lipid binding events converge to a similar value. These findings suggest a transition from nonannular to annular lipid binding to AmtB.

Time is of the Essence: Using Extended Hemin Treatment for a Case of Severe Acute Intermittent Porphyria.

Acute intermittent porphyria (AIP) is a disorder that affects heme synthesis, leading to accumulation of upstream precursors, and can cause an array of visceral and neurological symptoms. These can be severely debilitating and even fatal if not diagnosed and treated in a timely fashion. We outline a rare case of severe AIP masquerading as ascending polyneuropathy and how it was correctly diagnosed and treated with an extended course of hemin despite initial barriers to biochemical testing for AIP.

Language matters: humanizing service robots through the use of language during the COVID-19 pandemic.

Service robots are emerging quickly in the marketplace (e.g., in hotels, restaurants, and healthcare), especially as COVID-19-related health concerns and social distancing guidelines have affected people's desire and ability to interact with other humans. However, while robots can increase efficiency and enable service offerings with reduced human contact, prior research shows a systematic consumer aversion toward service robots relative to human service providers. This potential dilemma raises the managerial question of how firms can overcome consumer aversion and better employ service robots. Drawing on prior research that supports the use of language for building interpersonal relationships, this research examines whether the type of language (social-oriented vs. task-oriented language) a service robot uses can improve consumer responses to and evaluations of the focal service robot, particularly in light of consumers' COVID-19-related stress. The results show that consumers respond more favorably to a service robot that uses a social-oriented (vs. task-oriented) language style, particularly when these consumers experience relatively higher levels of COVID-19-related stress. These findings contribute to initial empirical evidence in marketing for the efficacy of leveraging robots' language style to improve customer evaluations of service robots, especially under stressful circumstances. Overall, the results from two experimental studies not only point to actionable managerial implications but also to a new avenue of research on service robots that examines customer-robot interactions through the lens of language and in contexts that can be stressful for consumers (e.g., healthcare or some financial service settings). Supplementary Information: The online version contains supplementary material available at 10.1007/s11002-022-09630-x.

Impact of Medicaid Expansion on Liver-Related Mortality.

BACKGROUND & AIMS: The Affordable Care Act provided the opportunity for states to expand Medicaid for low-income individuals. Not all states adopted Medicaid expansion, and the timing of adoption among expansion states varied. Prior studies have shown that Medicaid expansion improved mortality rates for several chronic conditions. Although there are data on the association between Medicaid expansion on insurance type among patients waitlisted for a liver transplant, there are no published data to date on its impact on liver disease-related mortality in the broader population. We therefore sought to evaluate the association between Medicaid expansion and state-level liver disease-related mortality using a quasi-experimental study design. METHODS: We evaluated age-adjusted, state-level, liver disease-related mortality rates using the Centers for Disease Control and Prevention data. We fit multivariable linear regression models that accounted for sociodemographic, clinical, and access-to-care variables at the state level, and a difference-in-difference estimator to evaluate the association between Medicaid expansion and liver disease-related mortality. RESULTS: In multivariable linear regression models, there was a significant association between Medicaid expansion and liver disease-related mortality (P = .02). Medicaid expansion was associated with 8.3 (95% CI, 1.6-15.1) fewer deaths from liver disease per 1,000,000 adult residents per year after Medicaid expansion compared with what would have been expected to occur if those states followed the same trajectory as nonexpansion states. The impact of Medicaid expansion translated to 870 fewer liver-related deaths per year in expansion states (4350 in the postexpansion study period from 2014 to 2018). CONCLUSIONS: These data support the contention that Medicaid expansion has been associated with significantly decreased liver disease-related mortality. Universal Medicaid expansion could further decrease liver disease-related mortality in the United States.

Entropy in the Molecular Recognition of Membrane Protein-Lipid Interactions.

Understanding the molecular driving forces that underlie membrane protein-lipid interactions requires the characterization of their binding thermodynamics. Here, we employ variable-temperature native mass spectrometry to determine the thermodynamics of lipid binding events to the human G-protein-gated inward rectifier potassium channel, Kir3.2. The channel displays distinct thermodynamic strategies to engage phosphatidylinositol (PI) and phosphorylated forms thereof. The addition of a 4'-phosphate to PI results in an increase in favorable entropy. PI with two or more phosphates exhibits more complex binding, where lipids appear to bind two nonidentical sites on Kir3.2. Remarkably, the interaction of 4,5-bisphosphate PI with Kir3.2 is solely driven by a large, favorable change in entropy. Installment of a 3'-phosphate to PI(4,5)P2 results in an altered thermodynamic strategy. The acyl chain of the lipid has a marked impact on binding thermodynamics and, in some cases, enthalpy becomes favorable.

Markov chains for modeling complex luminescence, absorption, and scattering in nanophotonic systems.

We developed a method to model fluorescence, absorption, and scattering in nanophotonic systems using ergodic Markov chains. Past works have used absorbing Markov chains to find the long-run angle-dependent distribution of emitted photons. In contrast, we use ergodic Markov chains to focus on the steady state distribution of photons within various media, giving additional insight into the macroscopic optical response during illumination. We show that the method reproduces Beer-Lambert's Law and Kirchhoff's Law, and can quantify deviations from these laws when their assumptions are violated. We also use the method to model luminescent solar concentrators (LSCs) based on semiconductor nanocrystals.

Liver Damage due to Hypervitaminosis.

Dietary supplements are unregulated medications that can lead to serious liver injury. Despite this, many people take vitamin supplements believing they are safe because they do not require prescriptions. We are reporting a case of an African American man who took large doses of vitamin supplements leading to noncirrhotic portal hypertension. The case highlights the importance of detailed history taking to diagnose and treat patients properly.

MicroRNA signature of cis-platin resistant vs. cis-platin sensitive ovarian cancer cell lines.

BACKGROUND: Ovarian cancer is the leading cause of death from gynecologic cancer in women worldwide. According to the National Cancer Institute, ovarian cancer has the highest mortality rate among all the reproductive cancers in women. Advanced stage diagnosis and chemo/radio-resistance is a major obstacle in treating advanced ovarian cancer. The most commonly employed chemotherapeutic drug for ovarian cancer treatment is cis-platin. As with most chemotherapeutic drugs, many patients eventually become resistant to cis-platin and therefore, diminishing its effect. The efficacy of current treatments may be improved by increasing the sensitivity of cancer cells to chemo/radiation therapies. METHODS: The present study is focused on identifying the differential expression of regulatory microRNAs (miRNAs) between cis-platin sensitive (A2780), and cis-platin resistant (A2780/CP70) cell lines. Cell proliferation assays were conducted to test the sensitivity of the two cell lines to cis-platin. Differential expression patterns of miRNA between cis-platin sensitive and cis-platin resistant cell lines were analyzed using novel LNA technology. RESULTS: Our results revealed changes in expression of 11 miRNAs out of 1,500 miRNAs analyzed. Out of the 11 miRNAs identified, 5 were up-regulated in the A2780/CP70 cell line and 6 were down regulated as compared to cis-platin sensitive A2780 cells. Our microRNA data was further validated by quantitative real-time PCR for these selected miRNAs. Ingenuity Pathway Analysis (IPA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was performed for the selected miRNAs and their putative targets to identify the potential pathways and networks involved in cis-platin resistance. CONCLUSIONS: Our data clearly showed the differential expression of 11 miRNAs in cis-platin resistant cells, which could potentially target many important pathways including MAPK, TGF-ß signaling, actin cytoskeleton, ubiquitin mediated proteasomal pathway, Wnt signaling, mTOR signaling, Notch signaling, apoptosis, and many other signaling pathways. Manipulation of one or more of these miRNAs could be an important approach for ovarian cancer chemotherapy.

An open-label study on the effect of flax seed powder (Linum usitatissimum) supplementation in the management of diabetes mellitus.

Diabetes mellitus is characterized by hyperglycemia and associated with aberrations in the metabolism of carbohydrate, protein, and lipid that result in development of secondary complications. Extensive studies have indicated that nutritional therapy plays a pivotal role in the controlling or postponing of development of these secondary complications. Several functional foods have been shown to possess hypoglycemic and hypolipidemic properties. Flax seed (FS) is a functional food that is rich in omega 3 fatty acids and antioxidants and is low in carbohydrates. In exploratory studies, FS was incorporated in recipes, which resulted in a reduction in the glycemic index of the food items. These observations prompted us to investigate the efficacy of FS supplementation in type 2 diabetics (n = 29). Subjects were assigned to the experimental (n = 18) or the control group (n = 11) on the basis of their desire to participate in the study. The experimental group's diet was supplemented daily with 10 g of FS powder for a period of 1 month. The control group received no supplementation or placebo. During the study, diet and drug intake of the subjects remained unaltered. The efficacy of supplementation with FS was evaluated through a battery of clinico-biochemical parameters. Supplementation with FS reduced fasting blood glucose by 19.7% and glycated hemoglobin by 15.6%. A favorable reduction in total cholesterol (14.3%), triglycerides (17.5%), low-density lipoprotein cholesterol (21.8%), and apolipoprotein B and an increase in high-density lipoprotein cholesterol (11.9%) were also noticed. These observations suggest the therapeutic potential of FS in the management of diabetes mellitus.

An open label study on the supplementation of Gymnema sylvestre in type 2 diabetics.

Diabetes mellitus is a complex metabolic disorder characterized by chronic hyperglycemia, and associated with long-term damage and dysfunction of various organs. Management of diabetes is therefore vital and involves maintaining euglycemia as much as possible by reducing blood glucose and by increasing insulin sensitivity and peripheral glucose uptake. Ayurveda has promoted the management of diabetes by regulating carbohydrate metabolism using several medicinal herbs, one of which is Gymnema sylvestre (GS). GS has been used in parts of India as a hypoglycemic agent and the results have been encouraging. Accordingly, we planned a quasi-experimental study to investigate the efficacy of the herb among type 2 diabetics. Patients enrolled from free-living population were purposively assigned to experimental or control groups, based on their willingness to participate in the study. The experimental group was supplemented with 500 mg of the herb per day for a period of 3 months, and the efficacy of the herb was assessed through a battery of clinical and biochemical tests. Supplementation of the diet with GS reduced polyphagia, fatigue, blood glucose (fasting and post-prandial), and glycated hemoglobin and there was a favorable shift in lipid profiles and in other clinico-biochemical tests. These findings suggest a beneficial effect of GS in the management of diabetes mellitus.