Adenine Group Research Articles

Omega-3 Fatty Acids Modify Drp1 Expression and Activate the PINK1-Dependent Mitophagy Pathway in the Kidney and Heart of Adenine-Induced Uremic Rats.

Mitochondrial homeostasis is controlled by biogenesis, dynamics, and mitophagy. Mitochondrial dysfunction plays a central role in cardiovascular and renal disease and omega-3 fatty acids (FAs) are beneficial for cardiovascular disease. We investigated whether omega-3 fatty acids (FAs) regulate mitochondrial biogenesis, dynamics, and mitophagy in the kidney and heart of adenine-induced uremic rats. Eighteen male Sprague Dawley rats were divided into normal control, adenine control, and adenine with omega-3 FA groups. Using Western blot analysis, the kidney and heart expression of mitochondrial homeostasis-related molecules, including peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), dynamin-related protein 1 (Drp1), and phosphatase and tensin homolog-induced putative kinase 1 (PINK1) were investigated. Compared to normal, serum creatinine and heart weight/body weight in adenine control were increased and slightly improved in the omega-3 FA group. Compared to the normal controls, the expression of PGC-1α and PINK1 in the kidney and heart of the adenine group was downregulated, which was reversed after omega-3 FA supplementation. Drp1 was upregulated in the kidney but downregulated in the heart in the adenine group. Drp1 expression in the heart recovered in the omega-3 FA group. Mitochondrial DNA (mtDNA) was decreased in the kidney and heart of the adenine control group but the mtDNA of the heart was recovered in the omega-3 FA group. Drp1, which is related to mitochondrial fission, may function oppositely in the uremic kidney and heart. Omega-3 FAs may be beneficial for mitochondrial homeostasis by activating mitochondrial biogenesis and PINK1-dependent mitophagy in the kidney and heart of uremic rats.

The selective chemical modification of the 6-amino group of adenosine of the premature termination codon induces readthrough to produce full-length peptide in the reconstituted E. Coli translation system

Nonsense mutations in the coding region turn amino acid codons into termination codons, resulting in premature termination codons (PTCs). In the case of the in-frame PTC, if translation does not stop at the PTC but continues to the natural termination codon (NTC) with the insertion of an amino acid, known as readthrough, the full-length peptide is formed, albeit with a single amino acid mutation. We have previously developed the functionality-transfer oligonucleotide (FT-Probe), which forms a hybrid complex with RNA of a complementary sequence to transfer the functional group, resulting in modification of the 4-amino group of cytosine or the 6-amino group of adenine. In this study, the FT-Probe was used to chemically modify the adenosines of the PTC (UAA, UAG, and UGA) of mRNA, which were assayed for the readthrough in a reconstituted Escherichia coli translation system. The third adenosine-modified UAA produced three readthrough peptides incorporating tyrosine, glutamine and lysine at the UAA site. It should be noted that the additional modification with a cyclodextrin only induced glutamine incorporation. The adenosine modified UGA induced readthrough very efficiently with selective tryptophan incorporation. Readthrough of the modified UGA is caused by inhibition of the RF2 function. This study has demonstrated that the chemical modification of the adenosine 6-amino group of the PTC is a strategy for effective readthrough in a prokaryotic translation system.

The Dissociation Process of NADP+ from NADPH-Cytochrome P450 Reductase Studied by Molecular Dynamics Simulation.

NADPH-cytochrome P450 reductase (CPR) plays a vital role as a redox partner for mammalian cytochrome P450 enzymes (P450s), facilitating the transfer of two electrons from NADPH to the P450 heme center in a sequential manner. Previous experimental studies revealed substantial domain movements of CPR, transitioning between closed and open states during the electron transfer (ET) cycle. These transitions are essential and are influenced by the binding of NADPH or the release of NADP+. However, the intricate molecular mechanisms governing the CPR-mediated ET cycle have largely remained elusive. This study employed molecular dynamics (MD) simulation techniques to explore the dissociation of NADP+ from CPR, a crucial step preceding the initial ET from CPR to a P450. Alongside the binding structure of NADP+ observed in a crystal structure (pose I), our MD simulations identified an alternative binding structure (pose II). Although pose II exhibits slightly lower stability than pose I, it can be formed through an approximate 210° counterclockwise rotation of the adenine group, with a free energy barrier of only 2.76 kcal/mol. The simulation results further suggest that NADP+ dissociation involves a tentative formation of pose II from pose I before complete dissociation, and that the binding of NADP+ to CPR is primarily governed by nonbonded interactions within the adenosine binding pocket.

Rigid-flexible mediated Co-polyimide enabling stable silicon anode in lithium-ion batteries

Silicon is considered as a promising electrode materials for the next generation of lithium-ion batteries. However, it’s commercial applications are hindered by significant volume changes. In this study, copolyimide binders with adjustable rigidity and flexibility were synthesized through simple copolymerization. The rigid segments containing adenine groups (p-APA) provide excellent mechanical strength and interface interaction, while flexible segments containing siloxane bonds and alkane chains (DS-NH2) can buffer volume changes through enhanced mobility and topological entanglement of molecular segments. Optimizing the copolymerization ratio helps minimize damage to the silicon electrode structure and stabilizes solid electrolyte interphase (SEI) growth. Compared to the rigid polyimide binders, rigid-flexible coupling strategy improves cycling stability, remaining a capacity of 2170 mAh/g at 2 A/g after 200 cycles and exhibiting stable cycling for over 750 cycles with a capacity limitation of 1500 mAh/g. The high mass loading silicon anodes, micron-sized silicon oxide electrodes and the full cells also exhibit favorable electrochemical performance. This research provides valuable insights for designing high-performance aromatic polymer binders for high energy density lithium-ion batteries.

Stable Interstrand Cross-Links Generated from the Repair of 1,N6-Ethenoadenine in DNA by α-Ketoglutarate/Fe(II)-Dependent Dioxygenase ALKBH2.

DNA cross-links severely challenge replication and transcription in cells, promoting senescence and cell death. In this paper, we report a novel type of DNA interstrand cross-link (ICL) produced as a side product during the attempted repair of 1,N6-ethenoadenine (εA) by human α-ketoglutarate/Fe(II)-dependent enzyme ALKBH2. This stable/nonreversible ICL was characterized by denaturing polyacrylamide gel electrophoresis analysis and quantified by high-resolution LC-MS in well-matched and mismatched DNA duplexes, yielding 5.7% as the highest level for cross-link formation. The binary lesion is proposed to be generated through covalent bond formation between the epoxide intermediate of εA repair and the exocyclic N6-amino group of adenine or the N4-amino group of cytosine residues in the complementary strand under physiological conditions. The cross-links occur in diverse sequence contexts, and molecular dynamics simulations rationalize the context specificity of cross-link formation. In addition, the cross-link generated from attempted εA repair was detected in cells by highly sensitive LC-MS techniques, giving biological relevance to the cross-link adducts. Overall, a combination of biochemical, computational, and mass spectrometric methods was used to discover and characterize this new type of stable cross-link both in vitro and in human cells, thereby uniquely demonstrating the existence of a potentially harmful ICL during DNA repair by human ALKBH2.

Adenine's impact on mice's gut and kidney varies with the dosage administered and relates to intestinal microorganisms and enzyme activities.

This study aimed to investigate the effects of different dosages of adenine on intestinal microorganisms and enzyme activities, laying the experimental groundwork for subsequent exploration of the microbial mechanisms underlying diarrhea with kidney yang deficiency syndrome. Twenty-four mice were assigned to the following four groups: the control (NC) group, low-dosage adenine (NML) group, middle-dosage adenine (NMM) group, and high-dosage adenine (NMH) group. Mice in the NML, NMM, and NMH groups received 25mg/(kg·d), 50mg/(kg·d), and 100mg/(kg·d) of adenine, respectively, 0.4mL/each, once a day for 14days. The NC group received 0.4mL sterile water. Parameters including body weight, rectal temperature, intestinal microorganisms, enzyme activities, and microbial activity were measured. Results indicated that mice in the experimental group displayed signs of a poor mental state, curled up with their backs arched, and felt sleepy and lazy, with sparse fur that was easily shed, and damp bedding. Some mice showed fecal adhesion contamination in the perianal and tail areas. Dosage-dependent effects were observed, with decreased food intake, body weight, rectal temperature, and microbial activity and increased water intake and fecal water content. Enzyme activity analyses revealed significantly higher activities of protease, sucrase, amylase, and cellulase in intestinal contents and lactase, sucrase, amylase, and cellulase in the mucosa of the NMM group compared to those of other groups. Ultimately, the higher adenine dosage was associated with more pronounced symptoms of kidney yang deficiency syndrome, with 50mg/kg adenine exhibiting the most substantial impact on the number of intestinal microbial colonies and enzyme activities.

Embryonic Ectoderm Development (EED) Inhibitor APG5918 Improves Chronic Kidney Disease- (CKD)-Induced Hemoglobin Insufficiency in Preclinical Models of Anemia

Introduction Anemia can be caused by infections, malignancies, CKD, or chemotherapy. Increasing Hb or fetal hemoglobin (HbF) can prevent or reduce anemia-related pathophysiology. Polycomb inhibitory complex 2 (PRC2), consisting of EZH2, EED, and SUZ12, is a subunit of the major transcriptional corepressor complex of BCL11A, and targeting EED may be one novel approach for treatment of patients with anemia. We report the effects of APG-5918, a small-molecule selective EED inhibitor, on Hb and HbF induction in human CD34⁺ hematopoietic stem cells (HSCs) and the efficacy of APG-5918 in a CKD-induced anemia model in vivo. Methods The pharmacodynamic (PD) effects of APG-5918 were evaluated in human cord blood CD34⁺ HSCs by flow cytometry, RT-qPCR, and ELISA. In vivo, the antianemia effect of APG-5918 was evaluated in adenine-induced renal anemic Sprague-Dawley rats. Results APG-5918 inhibited H3K27me3 inCD34⁺ HSCs, the critical epigenetic mark catalyzed by PRC2. APG-5918 also increased γ-globin coding gene ( HBG) and β-globin coding gene ( HBB) mRNA levels in a dose-dependent manner. After 7 days of treatment with APG-5918 at 1 μM, HBG and HBB mRNA increased to 12.36-fold and 4.76-fold of the control group, respectively, which was pharmacologically superior to effects observed with hydroxyurea at 33 µM (~6.53-fold and 2.27-fold increases in HBG and HBB mRNA, respectively). Hb and HbF protein were also upregulated in a dose-dependent manner. A total of 1.69-fold and 1.9-fold increases in HbF and Hb protein expression were observed after 7 days of treatment with APG-5918 at 1 μM.HbF and Hb protein showed no significant difference after hydroxyurea treatment. In an adenine-induced renal anemic rat model, APG-5918 was administered orally once daily at 3 dose levels (5, 15, and 45 mg/kg). Both body weight and the blood parameters erythrocytes, Hb, hematocrit (HCT), and reticulocytes (RET) improved significantly in a dose-dependent manner compared to the model (adenine) group ( p < 0.05, 0.01, or 0.001) (Figure 1). APG-5918 showed similar in vivo efficacy with erythropoietin (EPO): body weight and blood parameters in the group treated with APG-5918 45 mg/kg were comparable to those in the EPO group. In addition, blood parameters in the APG-5918 (15 mg/kg) plus EPO group recovered to the level of the control group, which was superior to the APG-5918 and EPO monotherapy groups. Conclusions APG-5918 demonstrated its effects as a single agent on inhibition of H3K27me3 inCD34⁺ HSCs, HbF and Hb induction, and normalization of hematologic parameters in a CKD-induced anemia model. APG-5918 also showed synergistic antianemia effects when combined with EPO. These findings support APG-5918 as a novel treatment option for CKD-induced anemia.

Effect of electroacupuncture on enteric neuronal autophagy in functional constipation mice.

To explore the effect mechanism of electroacupuncture (EA) on functional constipation (FC) at the combined lower he-sea and front-mu points of large intestine based on enteric neuronal autophagy. A total of 40 SPF Kunming mice were randomly divided into 5 groups (n = 8), i.e. a control group, a model group, an acupuncture group, a 3-methyl adenine (3-MA) group, and a 3-MA + acupuncture group. Except the control group, the FC model was established by gavage with compound diphenoxylate suspension for 14 days in the other 4 groups. After successful modeling, the mice of the acupuncture group and the 3-MA + acupuncture group received EA at bilateral "Tianshu" (ST 25) and "Shangjuxu" (ST 37), stimulated for 30 min with disperse-dense wave, 2 Hz/15 Hz of frequency, 1 mA of intensity. EA was delivered once daily. One course of treatment was composed of 5 days and 2 courses were needed, with an interval of 2 days. An intraperitoneal injection of 3-MA (15 mg/kg) was administered 30 min before EA in the mice of the 3-MA group and the 3-MA + acupuncture group, once daily. Before and after intervention, the time of the first black stool defecation and defecation behaviors in 6 h were observed in each group. After intervention, in every group, the small intestine propulsion rate was calculated, the colon tissue morphology was observed using HE staining, the ultrastructure of enteric neuronal autophagy was observed under transmission electron microscope, and the expressions of microtubule-associated protein 1 light chain 3 (LC3), Beclin-1 and neuronal nuclear antigen protein (NeuN) in neurons of colonic muscularis were determined by immunohistochemistry. Before intervention, when compared with those in the control group, the time of the first black stool defecation was prolonged (P<0.01, P<0.05), and numbers (P<0.01), wet weight (P<0.01, P<0.05) and water content (P<0.05, P<0.01) of stool in 6 h were reduced in the model, acupuncture, 3-MA and 3-MA + acupuncture groups. After intervention, compared with those in the control group, the time of the first black stool defecation was longer (P<0.05), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were decreased in the model group. The time of the first black stool defecation was shortened (P<0.01), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were increased in the acupuncture group when compared with those in the model group. The time of the first black stool defecation was extended (P<0.01), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were declined in the 3-MA + acupuncture group in comparison with those in the acupuncture group. All layers of colon tissue were normal and intact in each group. When compared with the control group, the small intestine propulsion rate and the average optical density (OD) values of LC3, Beclin-1 and NeuN in neurons of colonic muscularis were decreased (P<0.01), and autophagosomes were dropped in the model group. In the acupuncture group, the small intestine propulsion rate and the average OD values of NeuN, LC3 and Beclin-1 in neurons of colonic muscularis increased (P<0.01,P<0.05), and autophagosomes were elevated when compared with those in the model group. The small intestine propulsion rate and the average OD values of NeuN, LC3 and Beclin-1 in neurons of colonic muscularis were dropped (P<0.05,P<0.01) in the 3-MA + acupuncture group in comparison with those in the acupuncture group. Electroacupuncture may promote enteric neuronal autophagy and increase the number of neurons so that the intestinal motility can be improved and constipation symptoms can be relieved in FC mice.

Green Synthesis of Zinc Oxide-Nanoparticles from Ziziphus Spina-Christi Leaves Extract: Characterization and Their Protective Effects Against Liver Disturbances in Adenine-Exposed Male Rats

Zinc oxide nanoparticles (ZnO-NPs) have a significant feature due to their uses in various fields including medicine, biosensors, food additives, and electronic materials. This study aimed to the green synthesis of ZnO-NPs using aqueous extract of Ziziphus-spina christi leaves (Sider) and evaluates its protective roles against liver disorders after adenine-exposed male rats. Thirty-six male rats (3 months in age and weighing 200 ± 5 g) were randomly divided into 6 equal groups as following: Control adenine, Ziziphus-spina christi, ZnO-NPs, adenine + Ziziphus-spina christi and adenine + ZnO-NPs for 30 days. At the end of 30 days, the activity of (alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), superoxide dismutase (SOD) and concentrations of reduced glutathione (GSH) and nitric oxide (NO) were determined, as well as the liver histopathological alterations were investigated. Moreover, the body weight of all rats was measured over a week. The synthesized ZnO-NPs was characterized using several techniques. UV-Visible analysis showed a specific absorption peak at 362 nm. In Fourier Transform Infrared spectroscopy (FT-IR) absorption bands of Zn-O stretching bonding showed between 400 and 500 cm−1. Their crystallinity, hexagonal shape, size, and the specific surface area for the dry ZnO-NPs were also determined using the techniques of X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. Results showed significant decreases in ALT, AST and ALP in both groups adenine + Ziziphus-spina christi leaves extract and adenine + ZnO-NPs in comparison to the adenine group (p &lt; 0.05), as well as significant increases in body weight. Significant decrease was also demonstrated in NO level associated with an increase in SOD, and GSH. Based on these results, it can be said that ZnO-NPs and Ziziphus-spina christi leaves effectively protect against adenine-induced liver disorders, these were confirmed by improvements marked in histological changes of liver tissue of rats. GRAPHICAL ABSTRACT

Plasmon-Mediated Photoelectrochemical Hot-Hole Oxidation Coupling Reactions of Adenine on Nanostructured Silver Electrodes.

Surface-enhanced Raman spectroscopy (SERS) has been widely applied in the identification and characterization of DNA structures with high efficiency. Especially, the SERS signals of the adenine group have exhibited high detection sensitivity in several biomolecular systems. However, there is still no unanimous conclusion regarding the interpretation of some special kinds of SERS signals of adenine and its derivatives on silver colloids and electrodes. This Letter presents a new photochemical azo coupling reaction for adenyl residues, in which the adenine is selectively oxidized to (E)-1,2-di(7H-purin-6-yl) diazene (azopurine) in the presence of silver ions, silver colloids, and electrodes of nanostructures under visible light irradiation. The product, azopurine, is first found to be responsible for the SERS signals. This photoelectrochemical oxidative coupling reaction of adenine and its derivatives is promoted by plasmon-mediated hot holes and is regulated by positive potentials and pH of solutions, which opens up new avenues for studying azo coupling in the photoelectrochemistry of adenine-containing biomolecules on electrode surfaces of plasmonic metal nanostructures.

Insights into the Ozonation of Antiviral Purine Derivatives by the Basic Structures’ Kinetics and Ozone Consumption Ratios

Adenine and guanine derivatives are widely applied as antiviral agents. Due to their incomplete removal in conventional wastewater treatment, these substances were detected in the aquatic environment. Ozonation as an additional treatment step is known to degrade the antiviral compounds. However, oxidation mechanisms are still poorly examined. This study focused on the basic structures of the large group of antiviral nucleobase analogues, purine, adenine, and guanine. Their reaction with ozone allows prognoses of the ozonation of structurally related micropollutants. Therefore, these structures and the two antivirals acyclovir and penciclovir are investigated regarding their kinetics and degradation. Both characteristics are the basis for further research regarding the comprehensive understanding of the purines’ ozonation. Results show differences for the basic structures but similarities between guanine derivatives. Overall, the fundamental examinations exhibit a strong pH-dependency. Investigation of kinetics and ozone consumption ratios at pH 7 indicates ozone attack at nitrogen sites for purine (k < 8 × 10–2 M–1 s–1) and adenine (k = 100 M–1 s–1) with a slight shift to a C-C double bond at a higher pH for adenine. In guanine analogues (k = 3 × 104 M–1 s–1), the attack occurs mostly at carbon. Altogether, knowledge transfer to structurally related micropollutants is possible in the absence of additional strong electron-withdrawing or electron-donating substituents.

Tryptophan intake, not always the more the better.

To investigate the effects of excessive tryptophan intake on the body and the effects of tryptophan metabolism-related aryl hydrocarbon receptor (AhR) pathway in healthy rats and chronic kidney disease rats, to study the adverse effects of excess tryptophan. In Part I Experiment, the healthy rats were fed with diet containing 0.6, 1.2 and 1.8% tryptophan for 12 weeks. After the intervention, the blood and kidney tissues were collected. Serum creatinine and blood urea nitrogen were detected. Hematoxylin-eosin (H&E) staining was used to observe renal pathological changes. Enzyme-linked immunosorbent assay was used to detect serum kynurenic acid and AhR levels. The kidney levels of AhR, CyP1A1 and CyP1B1 were detected by western-blot. In Part II Experiment, the chronic kidney disease (CKD) model was induced by intra-gastric gavage with adenine for 4 weeks. Then the CKD rats were given tryptophan at a dose of 100 mg/kg or 500 mg/kg for eight weeks. Rat survival curve, renal function, renal tissue pathology and serum AhR were detected. Tryptophan-targeted ultra-high-performance liquid chromatography coupled with multiple reaction monitoring mass spectrometry (UHPLC-MRM-MS) was employed to quantitatively access the tryptophan-targeted metabolites in two parts experiments. In part I experiment, high tryptophan diet can increase the level of blood urea nitrogen (BUN) in healthy rats and induce focal renal tubulointerstitial injury. Tryptophan-targeted analyzes showed that high tryptophan diet feeding can significantly increase the concentration of kynurenine and indole metabolites. The serum AhR level and kidney AhR, CyP1A1 and CyP1B1 were also significantly increased in high tryptophan diet rats. In part II experiment, high tryptophan intervention induced a significant increase in mortality, serum creatinine, urea nitrogen levels, and renal pathological damage in CKD rats. The levels of tryptophan-targeted metabolites, kynurenine, xanthurenate, picolinic acid, 5-hydroxyindole-3-acetic acid, indole-3-lactic acid, indoleacetate and indoxyl sulfate, showed an upward trend in the high-dose tryptophan group (Ade + Trp-H) compared with the adenine group. The serum AhR of Ade + Trp-H rats was significantly higher than those of adenine rats. Moderate tryptophan intake may be beneficial, but excessive tryptophan can lead to accumulation of kynurenine and indole metabolites, activate AhR pathway and induce kidney injury.

Nanomolar Binding of an Antibiotic Peptide to DNA Measured with Raman Spectroscopy.

Immobilization of DNA to surfaces offers a convenient means of screening the binding affinity and selectivity of potential small-molecule therapeutic candidates. Unfortunately, most surface-sensitive methods for detecting these binding interactions are not informative of the molecular structure, information that is valuable for understanding the non-covalent interactions that stabilize binding. In this work, we report a method to meet this challenge by employing confocal Raman microscopy to quantify the association of a minor-groove-binding antimicrobial peptide, netropsin, to duplex DNA hairpin sequences immobilized on the interior surfaces of porous silica particles. To assess binding selectivity, particles functionalized with different sequences of DNA were equilibrated with solutions of 100 nM netropsin, and selective association was detected based on the presence of netropsin Raman scattering in the particles. The selectivity study revealed that netropsin binds to sequences of duplex DNA having AT-rich recognition regions. To quantify binding affinities, these AT-rich DNA sequences were equilibrated with a range of netropsin solution concentrations (1 to 100 nM). Raman scattering intensities of netropsin versus solution concentration were well described by single-binding-site Langmuir isotherms with nanomolar dissociation constants, in agreement with previous isothermal calorimetry and surface plasmon resonance results. Target sequence binding was accompanied with changes in netropsin and DNA vibrational modes consistent with the hydrogen bonding between the amide groups of netropsin and adenine and thymine bases in the DNA minor groove. The binding of netropsin to a control sequence lacking the AT-rich recognition region exhibited an affinity nearly 4 orders of magnitude weaker than found for the target sequences. The Raman spectrum of netropsin interacting with this control sequence showed broad pyrrole and amide mode vibrations at frequencies similar to a free solution, revealing less constrained conformations compared with the specific binding interactions observed with AT-rich sequences.

Vascular Calcification Exacerbates Abnormal Blood Pressure Variability in Chronic Kidney Disease: A “Two-Step” Study in Rats

Introduction: Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) with poor cardiovascular prognosis. The aim of this study was to explore the impact of VC on blood pressure variability (BPV) in animal models of CKD. Methods: Two optimal modelling methods, adenine high-phosphorus (HP) diet + calcitriol and 5/6 nephrectomy (Nx) + HP diet + calcitriol, for CKD-VC were chosen from the first-step experiment for the next step. A total of 36 male Wistar rats were randomly assigned to the standard-chow, sham-operated, adenine, 5/6Nx, adenine-VC, and 5/6Nx-VC groups. Continuous blood pressure (BP) measurement using the BP-2000 animal noninvasive BP analyser was started at the 9th week for the standard-chow, adenine, and adenine-VC groups and at the 7th week for the sham-operated, 5/6Nx, and 5/6Nx-VC groups. BPV metrics (BPVs), including the difference between maximum and minimum values, standard deviation, coefficient of variation, average real variability, and residuals derived from the generalized linear model of BP, were calculated. Results: The first experiment showed that the use of calcitriol accelerated the progression of VC in CKD rats (the modelling period was shortened from 16 weeks to 4–8 weeks) and confirmed the occurrence of VC at weeks 8 and 6 in the adenine-VC and 5/6Nx-VC groups, respectively. In the second experiment, 13 of 20 hour-to-hour BPVs increased significantly with the development of CKD and VC. BPV differences among the standard-chow, adenine, and adenine-VC groups were mainly due to the differences between the standard-chow and adenine-VC groups (7 of 10 BPVs were significantly different), followed by the differences between the standard-chow and adenine groups (3 of 10). BPV differences among the sham-operated, 5/6Nx, and 5/6Nx-VC groups were caused by the differences between the 5/6Nx-VC and 5/6Nx groups (4 of 10) or the 5/6Nx-VC and sham-operated groups (3 of 10). Conclusion: An increased BPV is observed in CKD rats, and VC further aggravates the abnormality of BPVs independent of CKD.

Decoding the Identification Mechanism of an SAM-III Riboswitch on Ligands through Multiple Independent Gaussian-Accelerated Molecular Dynamics Simulations.

S-Adenosyl-l-methionine (SAM)-responsive riboswitches play a central role in the regulation of bacterial gene expression at the level of transcription attenuation or translation inhibition. In this study, multiple independent Gaussian-accelerated molecular dynamics simulations were performed to decipher the identification mechanisms of SAM-III (SMK) on ligands SAM, SAH, and EEM. The results reveal that ligand binding highly affects the structural flexibility, internal dynamics, and conformational changes of SAM-III. The dynamic analysis shows that helices P3 and P4 as well as two junctions J23 and J24 of SAM-III are highly susceptible to ligand binding. Analyses of free energy landscapes suggest that ligand binding induces different free energy profiles of SAM-III, which leads to the difference in identification sites of SAM-III on ligands. The information on ligand-nucleotide interactions not only uncovers that the π-π, cation-π, and hydrogen bonding interactions drive identification of SAM-III on the three ligands but also reveals that different electrostatic properties of SAM, SAH, and EEM alter the active sites of SAM-III. Meanwhile, the results also verify that the adenine group of SAM, SAH, and EEM is well recognized by conserved nucleotides G7, A29, U37, A38, and G48. We expect that this study can provide useful information for understanding the applications of SAM-III in chemical, synthetic RNA biology, and biomedical fields.

Adenylate Kinase-Catalyzed Reactions of AMP in Pieces: Specificity for Catalysis at the Nucleoside Activator and Dianion Catalytic Sites.

The pressure to optimize the enzymatic rate acceleration for adenylate kinase (AK)-catalyzed phosphoryl transfer has led to the evolution of an induced-fit mechanism, where the binding energy from interactions between the protein and substrate adenosyl group is utilized to drive a protein conformational change that activates the enzyme for catalysis. The adenine group of adenosine contributes 11.8 kcal mol-1 to the total ≥14.7 kcal mol-1 adenosine stabilization of the transition state for AK-catalyzed phosphoryl transfer to AMP. The relative third-order rate constants for activation of adenylate kinase, by the C-5 truncated adenosine 1-(β-d-erythrofuranosyl)adenine (EA), for catalysis of phosphoryl transfer from ATP to phosphite dianion (HP, kcat/KHPKAct = 260 M-2 s-1), fluorophosphate (47 M-2 s-1), and phosphate (9.6 M-2 s-1), show that substitution of -F for -H and of -OH for -H at HP results, respectively, in decreases in the reactivity of AK for catalysis of phosphoryl transfer due to polar and steric effects of the -F and -OH substituents. The addition of a 5'-CH2OH to the EA activator results in a 3.0 kcal mol-1 destabilization of the transition state for AK-activated phosphoryl transfer to HP due to a steric effect. This is smaller than the 8.3 kcal mol-1 steric effect of the 5'-CH2OH substituent at OMP on HP-activated OMPDC-catalyzed decarboxylation of 1-(β-d-erythrofuranosyl)orotate. The 2'-OH ribosyl substituent shows significant interactions with the transition states for AK-catalyzed phosphoryl transfer from ATP to AMP and for adenosine-activated AK-catalyzed phosphoryl transfer from ATP to HP.

Adenine-functionalized conjugated polymer as an efficient photocatalyst for hydrogen evolution from water

Conjugated polymers have emerged as a promising class of organic photocatalysts for photocatalytic hydrogen evolution from water splitting due to their adjustable chemical structures and electronic properties. However, developing highly efficient organic polymer photocatalysts with high photocatalytic activity for hydrogen evolution remains a significant challenge. Herein, we present an efficient approach to enhance the photocatalytic performance of linear conjugated polymers by modifying the surface chemistry via introducing a hydrophilic adenine group into the side chain. The adenine unit with five nitrogen atoms could enhance the interaction between the surface of polymer photocatalyst and water molecules through the formation of hydrogen bonding, which improves the hydrophilicity and dispersity of the resulting polymer photocatalyst in the photocatalytic reaction solution. In addition, the strong electron-donating ability of adenine group with plentiful nitrogen atoms could promote the separation of light-induced electrons and holes. As a result, the adenine-functionalized conjugated polymer PF6A-DBTO2 shows a high photocatalytic activity with a hydrogen evolution rate (HER) of 25.21 mmol g−1 h−1 under UV-Vis light irradiation, which is much higher than that of its counterpart polymer PF6-DBTO2 without the adenine group (6.53 mmol g−1 h−1). More importantly, PF6A-DBTO2 without addition of a Pt co-catalyst also exhibits an impressive HER of 21.93 mmol g−1 h−1 under visible light (λ > 420 nm). This work highlights that it is an efficient strategy to improve the photocatalytic activity of conjugated polymer photocatalysts by the modification of surface chemistry.

Exogenous BMP7 administration attenuated vascular calcification and improved bone disorders in chronic uremic rats

Vascular calcification is commonly observed in chronic kidney disease (CKD) and is associated with increased morbidity and mortality. This study examined whether exogenous BMP7 administration can modulate disturbed CKD-MBD in adenine-induced chronic uremic rats. After an adenine diet for 4 weeks, the animals were injected with BMP7 for 2 weeks. Biochemical data, kidney tissue, bony structure, and vascular calcification of the thoracic aorta were examined and compared. Reduced renal function, hyperphosphatemia, and hyperparathyroidism with low 1,25(OH)2 vitamin D levels were observed in the adenine group. MicroCT revealed reduced bone mineral density (BMD), decreased bone and tissue volume ratio (BV/TV), and decreased trabecular number with increased separation. Marked vascular calcification was observed in adenine-fed animals, and immunohistochemical analysis showed increased expression of BMP2, RUNX2, vitamin D receptor (VDR), and Pit1 in aortic tissue. Treatment with BMP7 was associated with reduced serum phosphate, intact parathyroid hormone, FGF23, sclerostin, and DKK1 levels. BMP7 administration was accompanied with improvements in BMD and BV/TV. The increase in BMP2, RUNX2, VDR, and Pit1 was reversed by BMP7. In conclusion, exogenous BMP7 administration improved hyperphosphatemia and hyperparathyroidism in adenine-induced CKD. This treatment also attenuated vascular calcification and modulated structural abnormalities in the skeletal system.

Slow Rotational Dynamics of Cytosine NH2 Groups in Double-Stranded DNA.

Aromatic NH2 groups are essential as hydrogen-bond donors in secondary structures of DNA and RNA. Although rapid rotations of NH2 groups of adenine and guanine bases were previously characterized, there has been a lack of quantitative information about slow rotations of cytosine NH2 groups in Watson-Crick base pairs. In this study, using an NMR method we had recently developed, we determined the kinetic rate constants and energy barriers for cytosine NH2 rotations in a 15-base-pair DNA duplex. Our data show that the rotational dynamics of cytosine NH2 groups depend on local environments. Qualitative correlation between the ranges of 15N chemical shifts and rotational time scales for various NH2 groups of nucleic acids and proteins illuminates a relationship between the partial double-bond character of the C-N bond and the time scale for NH2 rotations.

S2 Heart Sound Detects Aortic Valve Calcification Independent of Hemodynamic Changes in Mice.

BackgroundCalcific aortic valve disease (CAVD) is often undiagnosed in asymptomatic patients, especially in underserved populations. Although artificial intelligence has improved murmur detection in auscultation exams, murmur manifestation depends on hemodynamic factors that can be independent of aortic valve (AoV) calcium load and function. The aim of this study was to determine if the presence of AoV calcification directly influences the S2 heart sound.MethodsAdult C57BL/6J mice were assigned to the following 12-week-long diets: (1) Control group (n = 11) fed a normal chow, (2) Adenine group (n = 4) fed an adenine-supplemented diet to induce chronic kidney disease (CKD), and (3) Adenine + HP (n = 9) group fed the CKD diet for 6 weeks, then supplemented with high phosphate (HP) for another 6 weeks to induce AoV calcification. Phonocardiograms, echocardiogram-based valvular function, and AoV calcification were assessed at endpoint.ResultsMice on the Adenine + HP diet had detectable AoV calcification (9.28 ± 0.74% by volume). After segmentation and dimensionality reduction, S2 sounds were labeled based on the presence of disease: Healthy, CKD, or CKD + CAVD. The dataset (2,516 S2 sounds) was split subject-wise, and an ensemble learning-based algorithm was developed to classify S2 sound features. For external validation, the areas under the receiver operating characteristic curve of the algorithm to classify mice were 0.9940 for Healthy, 0.9717 for CKD, and 0.9593 for CKD + CAVD. The algorithm had a low misclassification performance of testing set S2 sounds (1.27% false positive, 1.99% false negative).ConclusionOur ensemble learning-based algorithm demonstrated the feasibility of using the S2 sound to detect the presence of AoV calcification. The S2 sound can be used as a marker to identify AoV calcification independent of hemodynamic changes observed in echocardiography.