Structure/Function Relationships in Nickel-Peptide Complexes: Impact of the Primary Coordination Sphere on Square-Planar Nickel Chemistry

The novel metal-binding tripeptide asparagine-cysteine-cysteine (NCC) is capable of coordinating a metal ion, and we are exploring its use in several biological applications. Different metals may be incorporated into this tag, and when it is placed in line with a peptide or protein that has the potential to be used as a targeting agent, it has the potential to facilitate the diagnosis, treatment, and evaluation of cancers and other diseases. For example, platinum may be used as an anti-cancer therapeutic, whereas nickel generates a catalytic antioxidant. The advantage of this tag is that it is extremely small, is composed of naturally occurring amino acids, and binds metal with unique geometry. Metal binds irreversibly at physiological pH but is released upon modest acidification, as occurs with endocytosis. In order to utilize the tripeptide as a metal-binding tag, it is important to understand the structure, reactivity, and stability of this novel system. Initial studies with nickel established that NCC binds metal with 2N:2S geometry. Electronic absorption, circular dichroism (CD), and magnetic CD (MCD) data collected for Ni-NCC are consistent with a diamagnetic NiII center bound in square planar geometry. This complex acts as a mimic of the enzyme nickel superoxide dismutase (Ni-SOD), which catalyzes the disproportionation of superoxide to hydrogen peroxide and molecular oxygen. Changes in the CD signal of Ni-NCC indicate the optical activity of the complex changes over time, but mass spectrometry data show that the mass of the complex is unchanged, which suggests chiral rearrangement of the complex occurs. Performing the reaction in D2O allows incorporation of deuterium into non-exchangeable positions, indicating chiral inversion occurs at two of the alpha carbon atoms in the peptide. Control peptides were also used to verify the chirality of the final nickel-peptide complex is DLD-NCC. Characterization of the NCC sequence within a longer peptide shows that the geometry of metal coordination is maintained, though the electronic properties of the complex are varied to a small extent due to bis-amide coordination. Chiral inversion does not happen in the same two positions, though initial studies suggest inversion at a different location in the peptide may occur

Controlling the Chiral Inversion Reaction of the Metallopeptide Ni-Asparagine-Cysteine-Cysteine with Dioxygen

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/ic301717q.Synthetically generated metallopeptides have the potential to serve a variety of roles in biotechnology applications, but the use of such systems is often hampered by the inability to control secondary reactions. We have previously reported that the NiII complex of the tripeptide LLL-asparagine-cysteine-cysteine, LLL-NiII-NCC, undergoes metal-facilitated chiral inversion to DLD-NiII-NCC, which increases the observed superoxide scavenging activity. However, the mechanism for this process remained unexplored. Electronic absorption and circular dichroism studies of the chiral inversion reaction of NiII-NCC reveal a unique dependence on dioxygen. Specifically, in the absence of dioxygen, the chiral inversion is not observed, even at elevated pH, whereas the addition of O2 initiates this reactivity and concomitantly generates superoxide. Scavenging experiments using acetaldehyde are indicative of the formation of carbanion intermediates, demonstrating that inversion takes place by deprotonation of the alpha carbons of Asn1 and Cys3. Together, these data are consistent with the chiral inversion being dependent on the formation of a NiIII-NCC intermediate from NiII-NCC and O2. The data further suggest that the anionic thiolate and amide ligands in NiII-NCC inhibit Cα–H deprotonation for the NiII oxidation state, leading to a stable complex in the absence of O2. Together, these results offer insights into the factors controlling reactivity in synthetic metallopeptides

MAPping the Chiral Inversion and Structural Transformation of a Metal-Tripeptide Complex having Ni-SOD Activity

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/ic102295s.The metal abstraction peptide (MAP) tag is a tripeptide sequence capable of abstracting a metal ion from a chelator and binding it with extremely high affinity at neutral pH. Initial studies on the nickel-bound form of the complex demonstrate that the tripeptide asparagine-cysteine-cysteine (NCC) binds metal with 2N:2S, square planar geometry and behaves as both a structural and functional mimic of Ni superoxide dismutase (Ni-SOD). Electronic absorption, circular dichroism (CD), and magnetic CD (MCD) data collected for Ni-NCC are consistent with a diamagnetic NiII center. It is apparent from the CD signal of Ni-NCC that the optical activity of the complex changes over time. Mass spectrometry data show that the mass of the complex is unchanged. Combined with the CD data, this suggests that chiral rearrangement of the complex occurs. Following incubation of the nickel-containing peptide in D2O and back-exchange into H2O, incorporation of deuterium into non-exchangeable positions is observed, indicating chiral inversion occurs at two of the alpha carbon atoms in the peptide. Control peptides were used to further characterize the chirality of the final nickel-peptide complex, and DFT calculations were performed to validate the hypothesized position of the chiral inversions. In total, these data indicate Ni-SOD activity is increased proportionally to the degree of structural change in the complex over time, as cross-correlation between the change in CD signal and change in SOD activity reveals a linear relationship

A novel tripeptide model of nickel superoxide dismutase

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/ic901828m.Nickel superoxide dismutase (Ni-SOD) catalyzes the disproportionation of superoxide to molecular oxygen and hydrogen peroxide, but the overall reaction mechanism has yet to be determined. Peptide-based models of the 2N:2S nickel coordination sphere of Ni-SOD have provided some insight into the mechanism of this enzyme. Here we show that the coordination sphere of Ni-SOD can be mimicked using the tripeptide asparagine-cysteine-cysteine (NCC). NCC binds nickel with extremely high affinity at physiological pH with 2N:2S geometry, as demonstrated by electronic absorption and circular dichroism (CD) data. Like Ni-SOD, Ni-NCC has mixed amine/amide ligation that favors metal-based oxidation over ligand-based oxidation. Electronic absorption, CD, and magnetic CD data (MCD) collected for Ni-NCC are consistent with a diamagnetic Ni(II) center bound in square planar geometry. Ni-NCC is quasi-reversibly oxidized with a midpoint potential of 0.72(2) V (versus Ag/AgCl) and breaks down superoxide in an enzyme-based assay, supporting its potential use as a model for Ni-SOD chemistry

1H, 13C and 15N Backbone Assignment of the EC-1 Domain of Human E-Cadherin

The final publication is available at Springer via http://dx.doi.org/10.1007/s12104-013-9539-6The EC1 domain of E-cadherin has been shown to be important for cadherin-cadherin homophilic interactions. Cadherins are responsible for calcium-mediated cell-cell adhesion located at the adherens junction of the biological barriers (i.e., intestinal mucosa and the blood-brain barrier (BBB). Cadherin peptides can modulate cadherin interactions to improve drug delivery through the blood-brain barriers (BBB). However, the mechanism of modulating the E-cadherin interactions by cadherin peptides has not been fully elucidated. To provide a basis for subsequent examination of the structure and peptide-binding properties of the EC1 domain of human E-cadherin using solution NMR spectroscopy, the 1H, 13C and 15N backbone resonance of the uniformly labeled-EC1 were assigned and the secondary structure was determined based on the chemical shift values. These resonance assignments are essential for assessing protein-ligand interactions and are reported here

T Cell Activation and Senescence Predict Subclinical Carotid Artery Disease in HIV-Infected Women

Background. Individuals infected with human immunodeficiency virus (HIV) have increased risk of cardiovascular events. It is unknown whether T cell activation and senescence, 2 immunologic sequelae of HIV infection, are associated with vascular disease among HIV-infected adults

Prevalence of Microvascular and Macrovascular Disease in the Glycemia Reduction Approaches in Diabetes - A Comparative Effectiveness (GRADE) Study Cohort

Aims: The Glycemia Reduction Approaches in Diabetes - A Comparative Effectiveness (GRADE) trial is a randomized clinical trial comparing glycemic effects of four diabetes medications added to metformin in type 2 diabetes (T2D). Microvascular and macrovascular diseases are secondary outcomes. We evaluated the prevalence and risk factor relationships for microvascular and macrovascular complications in the GRADE cohort at study entry. Methods: Complication prevalence and risk factors were analyzed based on data from screening in all consenting participants meeting GRADE eligibility. Logistic regression and Z-statistics were used to assess risk factor relationships with complications. Results: We enrolled 5047 T2D participants [mean age 57 years; 36% female; mean known T2D duration 4 years (all < 10 years); mean HbA1c 8.0% (∼64 mmol/mol) at screening]. Urinary albumin/creatinine ratio (ACR) ≥ 30 mg/gram was present in 15.9% participants; peripheral neuropathy (by Michigan Neuropathy Screening Instrument) in 21.5%; cardiovascular autonomic neuropathy by electrocardiography-derived indices in 9.7%; self-reported retinopathy in 1.0%. Myocardial infarction ascertained by self-report or electrocardiogram was present in 7.3%, and self-reported history of stroke in 2.0%. Conclusions: In the GRADE cohort with < 10 years of T2D and a mean HbA1c of 8.0%, diabetes complications were present in a substantial fraction of participants, more so than might otherwise have been expected

Obeticholic acid for the treatment of non-alcoholic steatohepatitis: interim analysis from a multicentre, randomised, placebo-controlled phase 3 trial

Background Non-alcoholic steatohepatitis (NASH) is a common type of chronic liver disease that can lead to cirrhosis. Obeticholic acid, a farnesoid X receptor agonist, has been shown to improve the histological features of NASH. Here we report results from a planned interim analysis of an ongoing, phase 3 study of obeticholic acid for NASH. Methods In this multicentre, randomised, double-blind, placebo-controlled study, adult patients with definite NASH,non-alcoholic fatty liver disease (NAFLD) activity score of at least 4, and fibrosis stages F2–F3, or F1 with at least oneaccompanying comorbidity, were randomly assigned using an interactive web response system in a 1:1:1 ratio to receive oral placebo, obeticholic acid 10 mg, or obeticholic acid 25 mg daily. Patients were excluded if cirrhosis, other chronic liver disease, elevated alcohol consumption, or confounding conditions were present. The primary endpointsfor the month-18 interim analysis were fibrosis improvement (≥1 stage) with no worsening of NASH, or NASH resolution with no worsening of fibrosis, with the study considered successful if either primary endpoint was met. Primary analyses were done by intention to treat, in patients with fibrosis stage F2–F3 who received at least one dose of treatment and reached, or would have reached, the month 18 visit by the prespecified interim analysis cutoff date. The study also evaluated other histological and biochemical markers of NASH and fibrosis, and safety. This study is ongoing, and registered with ClinicalTrials.gov, NCT02548351, and EudraCT, 20150-025601-6. Findings Between Dec 9, 2015, and Oct 26, 2018, 1968 patients with stage F1–F3 fibrosis were enrolled and received at least one dose of study treatment; 931 patients with stage F2–F3 fibrosis were included in the primary analysis (311 in the placebo group, 312 in the obeticholic acid 10 mg group, and 308 in the obeticholic acid 25 mg group). The fibrosis improvement endpoint was achieved by 37 (12%) patients in the placebo group, 55 (18%) in the obeticholic acid 10 mg group (p=0·045), and 71 (23%) in the obeticholic acid 25 mg group (p=0·0002). The NASH resolution endpoint was not met (25 [8%] patients in the placebo group, 35 [11%] in the obeticholic acid 10 mg group [p=0·18], and 36 [12%] in the obeticholic acid 25 mg group [p=0·13]). In the safety population (1968 patients with fibrosis stages F1–F3), the most common adverse event was pruritus (123 [19%] in the placebo group, 183 [28%] in the obeticholic acid 10 mg group, and 336 [51%] in the obeticholic acid 25 mg group); incidence was generally mild to moderate in severity. The overall safety profile was similar to that in previous studies, and incidence of serious adverse events was similar across treatment groups (75 [11%] patients in the placebo group, 72 [11%] in the obeticholic acid 10 mg group, and 93 [14%] in the obeticholic acid 25 mg group). Interpretation Obeticholic acid 25 mg significantly improved fibrosis and key components of NASH disease activity among patients with NASH. The results from this planned interim analysis show clinically significant histological improvement that is reasonably likely to predict clinical benefit. This study is ongoing to assess clinical outcomes

Immunological insights into COVID-19 in Southern Nigeria

Introduction: One of the unexpected outcomes of the COVID-19 pandemic was the relatively low levels of morbidity and mortality in Africa compared to the rest of the world. Nigeria, Africa's most populous nation, accounted for less than 0.01% of the global COVID-19 fatalities. The factors responsible for Nigeria's relatively low loss of life due to COVID-19 are unknown. Also, the correlates of protective immunity to SARS-CoV-2 and the impact of pre-existing immunity on the outcome of the COVID-19 pandemic in Africa are yet to be elucidated. Here, we evaluated the natural and vaccine-induced immune responses from vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria throughout the three waves of the COVID-19 pandemic in Nigeria. We also examined the pre-existing immune responses to SARS-CoV-2 from samples collected prior to the COVID-19 pandemic. Methods: We used spike RBD and N- IgG antibody ELISA to measure binding antibody responses, SARS-CoV-2 pseudotype assay protocol expressing the spike protein of different variants (D614G, Delta, Beta, Omicron BA1) to measure neutralizing antibody responses and nucleoprotein (N) and spike (S1, S2) direct ex vivo interferon gamma (IFNγ) T cell ELISpot to measure T cell responses. Result: Our study demonstrated a similar magnitude of both binding (N-IgG (74% and 62%), S-RBD IgG (70% and 53%) and neutralizing (D614G (49% and 29%), Delta (56% and 47%), Beta (48% and 24%), Omicron BA1 (41% and 21%)) antibody responses from symptomatic and asymptomatic survivors in Nigeria. A similar magnitude was also seen among vaccinated participants. Interestingly, we revealed the presence of preexisting binding antibodies (N-IgG (60%) and S-RBD IgG (44%)) but no neutralizing antibodies from samples collected prior to the pandemic. Discussion: These findings revealed that both vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria make similar magnitude of both binding and cross-reactive neutralizing antibody responses. It supported the presence of preexisting binding antibody responses among some Nigerians prior to the COVID-19 pandemic. Lastly, hybrid immunity and heterologous vaccine boosting induced the strongest binding and broadly neutralizing antibody responses compared to vaccine or infection-acquired immunity alone

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure