Class Ib Research Articles

Thirty days clinical outcomes following stent implantation with aspirin-free prasugrel monotherapy in non-ST segment elevation myocardial infarction. Interim report from ASET-Japan pilot study

Abstract Background Dual antiplatelet therapy with a P2Y12 inhibitor, in addition to aspirin, is the standard therapy after percutaneous coronary intervention (PCI) for non-ST-segment elevation acute coronary syndrome (NSTE-ACS) to prevent ischemic cardiovascular events. The Acetyl-Salicylic Elimination Trial (ASET) pilot studies conducted in Japan in patients with NSTE-ACS investigated the safety and feasibility of a low-dose prasugrel monotherapy after PCI. Purpose To ensure the safety of the patients, enrolment in the study was implemented only after confirmation of a successful procedure. The abstract reports our interim analysis, aimed at evaluating preliminary safety and feasibility. Methods The ASET-Japan pilot study was designed to explore the feasibility and safety of a low dose of prasugrel monotherapy (3.75mg/day), without adjunctive aspirin, after optimal PCI using Everolimus eluting stent (EES) in Japanese patients with non-ST-segment elevation acute coronary syndromes. The primary endpoint in the ASET-Japan NSTE-ACS (Phase 2) is a 12-month clinical outcome. The study is currently in the follow-up phase. All the target lesions were treated with a platinum-chromium everolimus-eluting stent. The primary ischemic endpoint was the composite of cardiac death, spontaneous target vessel myocardial infarction, or definite stent thrombosis, and the primary bleeding endpoint was Bleeding Academic Research Consortium types 3 and 5 bleeding up to 12-month. If more than 3 events occurred, trial enrollment would have to be terminated by the data and safety monitoring board. Results One hundred one patients were enrolled after successful index PCI and completed a 30 days follow-up. The mean age was 69.1±12.3 years and 75.2% was male. The mean anatomical SYNTAX score was 7.9±4.7. Unstable angina (UAP) and NSTEMI were seen in 24.8% (25/101) and 75.2% (75/101) patients, respectively. According to the Braunwald classification, 8 percent of the patients were categorised as Class IA UAP, 48% as Class IB, 20% as Class IIB, 4% as Class IIIA and 20% as Class IIIB. In NSTEMI patients, the median (IQR) pre-procedural troponin value (cardiac Troponin T or I) was 2.79 (1.12 – 22.27) times the Upper Limit of Normal. According to the PRECISE DAPT score, 36.6% of patients were categorised as High Bleeding Risk (HBR) with scores above 25. At one month, the primary ischemic endpoints of cardiac death, target-vessel spontaneous MI or definite Stent thrombosis did not occur. Two patients (2.0%) had BARC type 3a bleeding. Conclusion Prasugrel monotherapy in the first 30 days following platinum-chromium everolimus-eluting stent deployment is a feasible and safe strategy in NSTE-ACS patients with simple anatomy and successful PCI.

Effects of SZV-2649, a new multiple ion channel inhibitor mexiletine analogue

The antiarrhythmic and cardiac electrophysiological effects of SZV-2649 that contains a 2,6-diiodophenoxy moiety but lacks the benzofuran ring system present in amiodarone, were studied in mammalian cell line, rat and dog cardiac preparations. SZV-2649 exerted antiarrhythmic effects against coronary artery occlusion/reperfusion induced ventricular arrhythmias in rats and in acetylcholine- and burst stimulation induced atrial fibrillation in dogs. SZV-2649 inhibited hERG and GIRK currents in HEK cells (IC50: 342 and 529 nM, respectively). In canine ventricular myocytes, SZV-2649 (10 µM) decreased the densities of IKr, and Ito outward and INaL and ICaL inward currents. The compound (2.5–10 µM) elicited Class IB type Vmax reducing and Class III type action potential duration prolonging effects in dog right ventricular muscle preparations. In canine atrial muscle, SZV-2629 (2.5–10 µM) moderately prolonged action potential duration and this effect was greatly augmented in preparations pretreated with 1 µM carbachol. In conclusion, SZV-2649, has antiarrhythmic effects based on its multiple ion channel blocking properties. Since its chemical structure substantially differs from that of amiodarone, it is expected that SZV-2649 would exhibit fewer adverse effects than the currently used most effective multichannel inhibitor drug amiodarone and may be a promising molecule for further development.

Stability of the Tyrosyl Radical in the Ribonucleotide Reductase Beta Subunit of Arcobacter bivalviorum

Arcobacter spp., such as Arcobacter bivalviorum (A. bivalviorum), are free-living organisms found in diverse environments and associated with animals. They are considered emerging enteropathogens and potential zoonotic agents. Ribonucleotide reductase (RNR) is the key enzyme that is used to convert ribonucleotides into deoxyribonucleoside triphosphates (dNTPs). This process utilises radical-based chemistry and is crucial for DNA biosynthesis and repair. There are three RNR classes, with class I RNR the most studied, present in A. bivalviorum, eukaryotes, and many prokaryotes. Class I RNRs are further divided into three subclasses: Ia, Ib, and Ic. Class Ib RNRs use a dimanganese-oxo centre, unlike class Ia RNRs, which use a diiron-oxo centre. A. bivalviorum possesses a class Ia enzyme that requires a diferric tyrosyl radical cofactor located within its beta (β) subunit. Indeed, both the efficiency and fidelity of DNA synthesis are influenced by the stability of the tyrosyl radical (Y•) in the RNR, which is a critical aspect of its enzymatic function. This study investigates the stability of the Y-radical (Y•) site within the RNR β subunit of A. bivalviorum and the nature of the neighbouring amino acid residues. To achieve these goals, we developed a model of the RNR β subunit of A. bivalviorum, using the RNR β subunit of Aquifex aeolicus as a reference template (7aik.1. A PDB). The results provide some important details about the radical site and its surrounding residues, highlighting the influence of the protein structure on the stability of the radical. These findings may guide the development of novel inhibitors targeting this enzyme in A. bivalviorum.

Treatment Adherence Rates and Long-Term Mortality in a Quaternary Multidisciplinary Heart Team: An Observational Cohort.

A multidisciplinary heart team (HT) approach to patients with complex coronary artery disease has a class IB recommendation, yet there are limited data on adherence to HT treatment recommendations and long-term clinical follow-up. The objective of this study was to assess adherence rates to HT recommendations and assess long-term mortality rates among patients with complex CAD. Six hundred eighty-four sequential HT cases for complex coronary artery disease from January 2015 to May 2017 were reviewed. After excluding cases with significant comorbid valve disease, baseline characteristics were compared based on HT treatment recommendations: optimal medical therapy, percutaneous coronary intervention, and coronary artery bypass grafting. Adherence rates were manually extracted, and 5-year mortality rates were obtained from the Michigan Death Registry. Seventy-two percent of 405 included patients were men (mean age 66±11 years), with high rates of medical comorbidities. Estimated surgical risk scores were lowest in the coronary artery bypass grafting group. Optimal medical therapy was recommended in 138 patients (34%), percutaneous coronary intervention in 95 (23%), and coronary artery bypass grafting in 172 (42%). Adherence to HT recommendations across groups was high (96%) and did not differ between treatment groups. Over 5 years of follow-up, there were 119 deaths, resulting in a cumulative mortality rate of 29%. In the largest HT cohort in the United States to date, high rates of adherence to HT recommendations were observed among high-risk patients with coronary artery disease. High rates of adherence to HT recommendations were observed irrespective of treatment group recommendation, suggesting that HT recommendations were individualized and acceptable to both patients and physicians alike.

Spectral and chemical characterization of amber from Xixia, Henan Province, China via FTIR, three-dimensional fluorescence spectra and Py (HMDS)-GC-MS

Xixia amber from Henan Province in China has undergone a thorough examination utilizing microscopic observation, infrared spectroscopy, and three-dimensional (3D) fluorescence spectroscopy. This systematic analysis has revealed that there are primarily two varieties of Xixia amber: a light-colored type and a dark-colored type. These can be differentiated based on their coloration, infrared spectra, and distinctive fluorescence attributes. Notably, the infrared spectral profile of Xixia amber features a prominent peak at 1023 cm−1, accompanied by less pronounced peaks at 1088 and 974 cm−1. These spectral characteristics set it apart from amber originating from the Baltic regions, Myanmar, and Fushun. Further distinction is achieved through 3D fluorescence spectra, where Xixia amber exhibits similarities to Burmese and Fushun ambers. Chemical classification via pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) identifies Xixia amber as belonging to Class Ib, characterized by its ordered structure and the absence of succinic acid. This comprehensive study delineates the coloration, infrared spectral properties, photoluminescent behavior, and chemical compositions of Xixia amber, clearly differentiating it from ambers sourced from other geographical locations.

Responsibility of The Sidenreng Rappang Religious Court Class IB Based on Maqāṣid Al-Sharīʻah in Reducing The Rate of Marriage Dispensation

This research aims to evaluate the responsibility of Sidenreng Rappang Class IB Religious Court in reducing the number of marriage dispensations. The study employs a qualitative approach with a case study method, involving in-depth interviews with judges, court officials, as well as families and couples applying for marriage dispensation. The findings of the study are as follows: 1) From 2019 to 2023, there has been a significant shift in the number of marriage dispensation applications at Sidenreng Rappang Class IB Religious Court. This shift indicates a change in societal perspectives on marriage values and the challenges they face in meeting marriage requirements. 2) Factors such as changes in family structure, increased social mobility, and the evolution of religious and cultural norms may contribute to this trend. Additionally, difficulties in meeting marriage requirements can drive individuals to seek dispensation. 3) The responsibility of Sidenreng Rappang Class IB Religious Court is also critical in preventing child marriages. The court's role includes tightening the examination of administrative requirements, providing explanations, exploring the genuine intentions of the child, and considering the true benefits and harms of child marriage

Designing Small Molecule PI3Kγ Inhibitors: A Review of Structure-Based Methods and Computational Approaches.

The PI3K/AKT/mTOR pathway plays critical roles in a wide array of biological processes. Phosphatidylinositol 3-kinase gamma (PI3Kγ), a class IB PI3K family member, represents a potential therapeutic opportunity for the treatment of cancer, inflammation, and autoimmunity. In this Perspective, we provide a comprehensive overview of the structure, biological function, and regulation of PI3Kγ. We also focus on the development of PI3Kγ inhibitors over the past decade and emphasize their binding modes, structure-activity relationships, and pharmacological activities. The application of computational technologies and artificial intelligence in the discovery of novel PI3Kγ inhibitors is also introduced. This review aims to provide a timely and updated overview on the strategies for targeting PI3Kγ.

MDB-89. DETERMINING THE IMMUNOMODULATORY POTENTIAL OF PI3KΓ IN AGGRESSIVE MEDULLOBLASTOMA AND THE TUMOR MICROENVIRONMENT

Abstract BACKGROUND Medulloblastoma (MB) is the most common pediatric embryonal brain tumor arising in the cerebellum. It has a “cold” tumor microenvironment (TME) characterized by an abundance of immunosuppressive Tumor Associated Macrophages (TAMs) and low T-cell infiltration. TAMs include tissue resident microglia and migrating bone marrow derived macrophages. While microglia play important roles in the central nervous system through their immune surveillance and ability to activate other immune cells, they can be polarized by tumor cells toward an anti-inflammatory state which allows for maintained tumor growth and proliferation. A potential new target to combat the immunosuppressed TME of MB is the class IB isoform PI3Kγ. Inhibiting this isoform has been attributed to controlling a critical switch between immune suppression and immune stimulation in TAMs but has yet to be examined in MB and its TME. We hypothesize that inhibiting PI3Kγ in TAMs and MB tumor cells will induce an anti-tumorigenic immune response within the MB TME and promote tumor clearance. METHODS Engineered murine MB cells, mCB DNp53 MYC, are treated with a pan-PI3K or specific PI3Kγ inhibitor for 48 hours before being co-cultured with naïve splenic CD4 T-cells from C57BL/6J mice for 5 days. Proliferation of the T cells is measured using Cell Trace Violet through flow cytometry on a Cytek Aurora. RESULTS Pan-PI3K inhibition revealed that tumor cells treated with the inhibitor prior to co-culturing did not suppress T-cell proliferation as drastically when compared to untreated tumor cells. Treatment with a selective inhibitor is on-going. CONCLUSIONS These results suggest that inhibition of the PI3K pathway in our MB tumor cells dampens their ability to suppress T cell proliferation. The PI3K pathway may play an active role in tumor cell’s ability to induce immunosuppression. Inhibiting this pathway may be a new avenue for therapeutic intervention for relapsed/refractory MB.

Identification and analysis of immunogenicity and immunotherapy efficacy by fatty acid genes: a novel prognostic features of lumbar disc herniation and Mendelian randomization analysis

ABSTRACT Background: Sciatica is a phrase used to describe radiating leg discomfort. The most common cause is lumbar disc herniation (LDH), which is considered to start in the nucleus pulposus. Advancements in lipidomics and metabolomics have unveiled the complex role of fatty acid metabolism (FAM) in both healthy and pathological states. However, the specific roles of fatty acid metabolism-related genes (FAMGs) in shaping therapeutic approaches, especially in LDH, remain largely unexplored and are a subject of ongoing research. Methods: The junction of the weighted correlation network analysis (WGCNA) test with 6 FAMGs enabled the finding of FAMGs. Gene set variation analysis (GSVA) was used to identify the possible biological activities and pathways of FAMGs. LASSO was used to determine diagnostic effectiveness of the four FAMGs in diagnosing LDH. GSE124272, GSE147383, GSE150408, and GSE153761 were utilized to confirm the levels of expression of four FAMGs. Results: Four FAMGs were discovered [Acyl-CoA Thioesterase 4 (ACOT4), Cytochrome P450 Family 4 Subfamily A Member 11 (CYP4A11), Acyl-CoA Dehydrogenase Long Chain (ACADL), Enoyl-CoA Hydratase and 3-Hydroxyacyl CoA Dehydrogenase (EHHADH)] For biological function analysis, mhc class ib receptor activity, response to thyroxine, response to l phenylalanine derivative were emphasized. Conclusions: FAMGs can help with prognosis and immunology, and provide evidence for fatty acid metabolism-related targeted therapeutics. In LDH, FAMGs and their interactions with immune cells might be therapeutic targets.

Preparation and characterization of MnIIMnIII complexes with relevance to class Ib ribonucleotide reductases

The Mn2 complex [MnII2(TPDP)(O2CPh)2](BPh4) (1, TPDP = 1,3-bis(bis(pyridin-2-ylmethyl)amino)propan-2-ol, Ph =phenyl) was prepared and subsequently characterized via single-crystal X-ray diffraction, X-ray absorption, electronic absorption, and infrared spectroscopies, and mass spectrometry. 1 was prepared in order to explore its properties as a structural and functional mimic of class Ib ribonucleotide reductases (RNRs). 1 reacted with superoxide anion (O2•–) to generate a peroxido-MnIIMnIII complex, 2. The electronic absorption and electron paramagnetic resonance (EPR) spectra of 2 were similar to previously published peroxido-MnIIMnIII species. Furthermore, X-ray near edge absorption structure (XANES) studies indicated the conversion of a MnII2 core in 1 to a MnIIMnIII state in 2. Treatment of 2 with para-toluenesulfonic acid (p-TsOH) resulted in the conversion to a new MnIIMnIII species, 3, rather than causing O—O bond scission, as previously encountered. 3 was characterized using electronic absorption, EPR, and X-ray absorption spectroscopies. Unlike other reported peroxido-MnIIMnIII species, 3 was capable of oxidative O—H activation, mirroring the generation of tyrosyl radical in class Ib RNRs, however without accessing the MnIIIMnIV state.

Successful Use of Lidocaine in the Management of Severe Flécaïne Poisoning Refractory to Conventional Treatment

Introduction: Intoxications with class Ic antiarrhythmics, such as flécaïne, are rare but potentially life-threatening. We report a case of severe flécaïne poisoning where the use of lidocaine, a class Ib antiarrhythmic, enabled effective management of refractory rhythm disturbances. Methods: A 22-year-old female patient was admitted for voluntary flécaïne poisoning after ingesting 2 g. She presented with shock, ventricular fibrillation, and torsades de pointes refractory to conventional treatment (cardioversion, magnesium sulfate, bicarbonates, amiodarone). Results: After initial treatment failure, a lidocaine loading dose successfully resolved refractory ventricular rhythm disturbances. Continuous administration of lidocaine subsequently stabilized the patient's hemodynamic status and reduced the need for vasopressors. Discussion: While the use of lidocaine is traditionally contraindicated in poisoning with class Ic antiarrhythmics due to the risk of drug interactions, this case demonstrates its potential value in refractory situations. Lidocaine may have a competitive effect on sodium channels, thereby reversing the toxicity of potent inhibitors such as flécaïne. Conclusion: In severe flécaïne poisoning refractory to conventional treatment, the use of lidocaine can be a life-saving therapeutic option when extracorporeal clearance techniques are not available.

To Evaluate the Relationship between Maxillary and Mandibular Base Lengths with Dental Crowding in Different Skeletal Malocclusions

Introduction Exploring the relationship between arch dimensions and crowding has long been a topic of interest. Many studies have found significant relationship between the two, while others have suggested that crowding is a multifactorial condition and is not dependent on arch dimensions only. Objective To evaluate the relationship as well as sexual dimorphism between maxillary and mandibular skeletal base lengths with dental crowding in different skeletal malocclusions. Materials and Methods The sample comprised 100 orthodontic patients (49 males, 51 females), which were divided into three groups based on the anteroposterior relationship of maxilla with the mandible. Each group was subdivided based on the severity of mandibular and maxillary arch crowding into two subgroups, and each subgroup was further divided into male and female subjects. Measurements of maxillary and mandibular base lengths (Co-A and Co-Gn) and tooth size arch length discrepancies were obtained through lateral cephalograms and dental casts, respectively, and measurements obtained were analyzed statistically. Results Patients with class IB, IIB, and IIIB had significantly smaller maxillary and mandibular base lengths than subjects with class IA, IIA, and IIIA. A weak negative correlation was found between maxillary base length and maxillary crowding with r = –0.451 and p = .000, while a strong positive correlation was observed between maxillary and mandibular crowding with r = 0.742 and p = .000. Conclusion An inverse correlation exists between dental crowding and the lengths of maxillary and mandibular bases, regardless of skeletal malocclusion.

Negative MRI and a seizure onset zone close to eloquent areas in FCD type II: Application of MRg-LiTT after a SEEG re-evaluation in pediatric patients with a previous failed surgery

ObjectiveNegative MRI and an epileptogenic zone (EZ) adjacent to eloquent areas are two main issues that can be encountered during pre-surgical evaluation for epilepsy surgery. Focal Cortical Dysplasia type II (FCD type II) is the most common aetiology underlying a negative MRI.The objective of this study is to present three cases of pediatric patients exhibiting negative MRI and a seizure onset zone close to eloquent areas, who previously underwent traditional open surgery or SEEG-guided radiofrequency thermocoagulations (RF-TC). After seizure seizure recrudescence, pre-surgical SEEG was re-evaluated and Magnetic Resonance-guided laser interstitial thermal therapy (MRg-LiTT) was performed.We discuss the SEEG patterns, the planning of laser probes trajectories and the outcomes one year after the procedure. MethodsPediatric patients who underwent SEEG followed by MRg-LiTT for drug-resistant epilepsy associated with FCD type II at our Centre were included. Pre-surgical videoEEG (vEEG), stereoEEG (sEEG), and MRI were reviewed. Post-procedure clinical outcome (measured by Engel score) and complications rates were evaluated. ResultsThree patients underwent 3 MRg-LiTT procedures from January 2022 to June 2022. Epileptogenic zone was previously studied via SEEG in all the patients. All the three patients pre-surgical MRI was deemed negative. Mean age at seizure onset was 47 months (21–96 months), mean age at MRg-LiTT was 12 years (10 years 10 months – 12 years 9 months). Engel class Ia outcome was achieved in patients #2 and #3, Engel class Ib in patient #1. Mean follow-up length was of 17 months (13 months – 20 months). Complications occurred in one patient (patient #2, extradural hematoma). ConclusionsThe combined use of SEEG and MRg-LiTT in complex cases can lead to good outcomes both as a rescue therapy after failed surgery, but also as an alternative to open surgery after a successful SEEG-guided Radiofrequency Thermocoagulation (RF-TC). Specific SEEG patterns and a previous good outcome from RF-TC can be predictors of a favourable outcome.

Class Ib Ribonucleotide Reductases: Activation of a Peroxido-MnIIMnIII to Generate a Reactive Oxo-MnIIIMnIV Oxidant.

In the postulated catalytic cycle of class Ib Mn2 ribonucleotide reductases (RNRs), a MnII2 core is suggested to react with superoxide (O2·-) to generate peroxido-MnIIMnIII and oxo-MnIIIMnIV entities prior to proton-coupled electron transfer (PCET) oxidation of tyrosine. There is limited experimental support for this mechanism. We demonstrate that [MnII2(BPMP)(OAc)2](ClO4) (1, HBPMP = 2,6-bis[(bis(2 pyridylmethyl)amino)methyl]-4-methylphenol) was converted to peroxido-MnIIMnIII (2) in the presence of superoxide anion that converted to (μ-O)(μ-OH)MnIIIMnIV (3) via the addition of an H+-donor (p-TsOH) or (μ-O)2MnIIIMnIV (4) upon warming to room temperature. The physical properties of 3 and 4 were probed using UV-vis, EPR, X-ray absorption, and IR spectroscopies and mass spectrometry. Compounds 3 and 4 were capable of phenol oxidation to yield a phenoxyl radical via a concerted PCET oxidation, supporting the proposed mechanism of tyrosyl radical cofactor generation in RNRs. The synthetic models demonstrate that the postulated O2/Mn2/tyrosine activation mechanism in class Ib Mn2 RNRs is plausible and provides spectral insights into intermediates currently elusive in the native enzyme.

Implementasi Observasi Profiling Peserta Didik sebagai Persiapan Perencanaan Pembelajaran di Kelas IB SDN Gayamsari 02 Semarang

The study aimed to (1) map the learning styles of students in class IB at SDN Gayamsari 02 Semarang, and (2) design a learning approach aligned with the observed student profiles. The research method used was descriptive qualitative. The population in this study included all grade 1 students at SD Negeri Gayamsari 02 Semarang, with the research sample being Class IB, consisting of 26 students, 13 female and 13 male. The research stages involved planning, implementation, and reflection. Observation results indicated that the designed learning approach did not effectively accommodate the diverse student characteristics in the class. Preparation of the learning design began with observing student profiles, mapping learning styles, and planning methods and approaches in line with all student learning modalities. The learning design included the use of the Teaching at The Right Level (TaRL) approach, the Problem Based Learning (PBL) model, and the Timeboard media in class IB at SD Negeri Gayamsari 02 Semarang. Reflection activities were conducted to identify and evaluate inappropriate learning designs.

Instability of the HLA-E peptidome of HIV presents a major barrier to therapeutic targeting

Naturally occurring Tcells that recognize microbial peptides via HLA-E, a nonpolymorphic HLA class Ib molecule, could provide the foundation for new universal immunotherapeutics. However, confidence in the biological relevance of putative ligands is crucial, given that the mechanisms by which pathogen-derived peptides can access the HLA-E presentation pathway are poorly understood. We systematically interrogated the HIV proteome using immunopeptidomic and bioinformatic approaches, coupled with biochemical and cellular assays. No HIV HLA-E peptides were identified by tandem mass spectrometry analysis of HIV-infected cells. In addition, all bioinformatically predicted HIV peptide ligands (>80) were characterized by poor complex stability. Furthermore, infected cell elimination assays using an affinity-enhanced Tcell receptor bispecific targeted to a previously reported HIV Gag HLA-E epitope demonstrated inconsistent presentation of the peptide, despite normal HLA-E expression on HIV-infected cells. This work highlights the instability of the HIV HLA-E peptidome as a major challenge for drug development.

The Influence of Motivation and Work Discipline on Employee Performance at the Class IB Religious Court Office in Martapura Banjar Regency

The Influence of Motivation and Work Discipline on Employee Performance at the Class IB Religious Court Office in Martapura Banjar Regency

Luminosity class of the symbiotic stars 4U1954+319 and ZZ CMi

We performed optical photometry and spectral observations of the symbiotic stars 4U1954+319 and ZZ CMi. For 4U1954+319, using high-resolution spectra, we, measure the equivalent widths of diffuse interstellar bands (DIBs) and estimate the interstellar reddening E(B-V ) = 0:83?0:09. Using the GAIA distances and our photometry, we find: (1) the absolute V -band magnitude MV =-5:23 ? 0:08 of 4U1954+319 and that the mass donor is a supergiant of luminosity class Ib, and (2) MV = -0:27?0:2 for ZZ CMi and that the mass donor is a giant of luminosity class III.

Structural insights into the initiation of free radical formation in the Class Ib ribonucleotide reductases in Mycobacteria

Class I ribonucleotide reductases consisting of α and β subunits convert ribonucleoside diphosphates to deoxyribonucleoside diphosphates involving an intricate free radical mechanism. The generation of free radicals in the Class Ib ribonucleotide reductases is mediated by di-manganese ions in the β subunits and is externally assisted by flavodoxin-like NrdI subunit. This is unlike Class Ia ribonucleotide reductases, where the free radical generation is initiated at its di-iron centre in the β subunits with no external support from another subunit. Class 1b ribonucleotide reductase complex is an essential enzyme complex in the human pathogen Mycobacterium tuberculosis and its structural details are largely unknown. In this study we have determined the crystal structures of Mycobacterial NrdI in oxidised and reduced forms, and similarly those of NrdF2:NrdI complexes. These structures provide detailed atomic view of the mechanism of free radical generation in the β subunit in this pathogen. We observe a well-formed channel in NrdI from the surface leading to the buried FMN moiety and propose that oxygen molecule accesses FMN through it. The oxygen molecule is further converted to a superoxide ion upon electron transfer at the FMN moiety. Similarly, a path for superoxide radical transfer between NrdI and NrdF2 is also observed. The oxidation of Mn(II) in NrdF2I to high valent oxidation state (either Mn(III) or Mn(IV) assisted by the reduced FMN site was evidently confirmed by EPR studies. SEC-MALS and low resolution cryo-EM map indicate unusual stoichiometry of 2:1 in the M. tuberculosis NrdF2I complex. A density close to Tyr 110 at a distance <2.3 Å is observed, which we interpret as OH group. Overall, the study therefore provides important clues on the initiation of free radical generation in the β subunit of the ribonucleotide reductase complex in M. tuberculosis.

Proving Learning Outcomes in Mathematic of Long Addition and Subtraction Materials through the Cooperative Learning Type Jigsaw Model Class IB Islamic Elementary School An-Nuriyah

Based on the learning results of first grade students of SDS Ialam An-Nuriyah Jagakarsa South Jakarta, it shows that the results of learning Mathematics about addition and subtraction in long series are still below the specified KKM which is 70. Of the 25 students, only 8 students were able to reach the KKM, while 17 students were declared not to have reached the KKM score. In line with this, an improvement in learning Mathematics about addition and subtraction using the cooperative learning type jigsaw model was carried out. The purpose of this study was to improve the learning outcomes of IB grade students on long addition and subtraction. This research uses a class action research method that uses a cycle system consisting of planning, implementation, observation and reflection. Based on the results of the study, in the pre-cycle students whose learning completeness was above KKM 70 were only 8 students or (36.0%) out of 25 students. In cycle 1 it increased to 14 students or (56.0%) out of 25 students. While in cycle 2 it increased to 24 students or (96.0%) of 25 students. This means that the class learning completeness has been achieved because it has exceeded the target of the predetermined success indicator of 80%. The conclusion is that using the jigsaw type cooperative learning model on long addition and subtraction material can improve student learning outcomes.