Identifying the neural marker of chronic sciatica using multimodal neuroimaging and machine learning analyses.

Introduction: Sciatica is a pain disorder often caused by the herniated disk compressing the lumbosacral nerve roots. Neuroimaging studies have identified functional abnormalities in patients with chronic sciatica (CS). However, few studies have investigated the neural marker of CS using brain structure and the classification value of multidimensional neuroimaging features in CS patients is unclear. Methods: Here, structural and resting-state functional magnetic resonance imaging (fMRI) was acquired for 34 CS patients and 36 matched healthy controls (HCs). We analyzed cortical surface area, cortical thickness, amplitude of low-frequency fluctuation (ALFF), regional homogeneity (REHO), between-regions functional connectivity (FC), and assessed the correlation between neuroimaging measures and clinical scores. Finally, the multimodal neuroimaging features were used to differentiate the CS patients and HC individuals by support vector machine (SVM) algorithm. Results: Compared to HC, CS patients had a larger cortical surface area in the right banks of the superior temporal sulcus and rostral anterior cingulate; higher ALFF value in the left inferior frontal gyrus; enhanced FCs between somatomotor and ventral attention network. Three FCs values were associated with clinical pain scores. Furthermore, the three multimodal neuroimaging features with significant differences between groups and the SVM algorithm could classify CS patients and HC with an accuracy of 90.00%. Discussion: Together, our findings revealed extensive reorganization of local functional properties, surface area, and network metrics in CS patients. The success of patient identification highlights the potential of using artificial intelligence and multimodal neuroimaging markers in chronic pain research.

Acupuncture for chronic sciatica: protocol for a multicenter randomised controlled trial.

BACKGROUND: Chronic Sciatica is a disabling condition causing considerable medical, social and financial implications. Currently, there is no recognised long-term effective treatment to alleviate sciatica. Acupuncture has been widely used for treating chronic pains with persistent analgesic effects. We aim to evaluate the efficacy and safety of acupuncture for chronic sciatica with follow-up in 52 weeks. METHODS AND ANALYSIS: This is a multicenter randomised sham-controlled trial. A total of 216 patients with chronic sciatica will be enrolled and randomly assigned to the acupuncture or sham acupuncture group. There will be 10 treatment sessions applied in 4 weeks with frequency decreased over time. Patients will complete follow-ups during 52 weeks. The primary outcomes are changes in leg pain intensity and disability from baseline to week 4. Secondary outcomes include back pain intensity, frequency and bothersomeness, quality of life, and global perceived effect. Adverse events will be recorded in detail. ETHICS AND DISSEMINATION: Ethical approval of this trial was granted from the ethics committee of Beijing University of Chinese Medicine and all study centres (No. 2020BZYLL0803). Written informed consent will be obtained from enrolled patients. Trial results will be disseminated in peer-reviewed publications. TRIAL REGISTRATION NUMBER: ChiCTR2100044585 (Chinese Clinical Trial Registry, http://www.chictr.org.cn, registered on 24 March 2021); preresults.

Is acupuncture effective for knee osteoarthritis? A protocol for a systematic review and meta-analysis.

INTRODUCTION: Knee osteoarthritis (KOA) is one of the leading causes of disability. The effectiveness of acupuncture for treating KOA remains controversial. This protocol describes the method of a systematic review and meta-analysis evaluating the effectiveness and safety of acupuncture for treating KOA. METHODS AND ANALYSIS: Four English databases (PubMed, Embase, Cochrane Library databases and Web of Science) and four Chinese databases (China National Knowledge Infrastructure, Chinese Biomedical Literature Database, VIP Database for Chinese Technical Periodicals, and Wanfang) will be searched from the database inception to 1 September 2021. All randomised controlled trials related to acupuncture for KOA will be included. Extracted data will include publication details, basic information, demographic data, intervention details and patient outcomes. The primary outcome will be pain intensity. Risk of bias will be assessed using the Cochrane Collaboration's tool for assessing risk of bias. Article selection, data extraction and risk of bias assessment will be performed in duplicate by two independent reviewers. If the meta-analysis is precluded, we will conduct a descriptive synthesis using a best-evidence synthesis approach. The strength of recommendations and quality of evidence will be assessed using the Grading of Recommendations Assessment Development and Evaluation working group methodology. ETHICS AND DISSEMINATION: Ethics approval is not required because individual patient data are not included. This protocol was registered in the international Prospective Register of Systematic Reviews on 25 February 2021. The systematic review and meta-analysis will be submitted for publication in a peer-reviewed journal. The findings will also be disseminated through conference presentations. TRIAL REGISTRATION NUMBER: CRD42021232177.

[Application of "patient and public involvement" in acupuncture clinical research].

In order to explore the application of "patient and public involvement" (PPI) in acupuncture clinical research, the connotation, reporting standards and research status of PPI at home and abroad are collated, and the key problems of PPI encountered in acupuncture clinical research are deeply considered and summarized. It is suggested that the short-form checklist of the Guidance for Reporting Involvement of Patients and the Public (GRIPP) of the 2nd edition should be applied to acupuncture clinical research. PPI provides a new perspective for acupuncture clinical research. It is beneficial for each stage of research, contributes to the improvement of acupuncture medical service mode and increases the success rate and cost-effectiveness of research so that the innovation and development of acupuncture science can be promoted.

Evaluating the efficacy and safety of electro-acupuncture in patients with antipsychotic-related constipation: protocol for a randomized controlled trial.

BACKGROUND: Constipation is known as a common adverse effect of antipsychotics. Advice for its management remains inadequate. This study is designed to investigate the efficacy and safety of electro-acupuncture (EA) for antipsychotic-related constipation. METHODS: This is a single-centric, parallel-group, randomized controlled trial with blinded participants, outcome assessor, and statistician. One hundred twelve participants will be randomly assigned into the EA group or sham acupuncture (SA) group in a 1:1 ratio. The study will last for 22 weeks for each participant, including a 2-week baseline assessment period, an 8-week treatment period, and a follow-up for 12 weeks. The primary outcome is the change of mean weekly complete spontaneous bowel movements (CSBMs) during weeks 1 to 8 from baseline. Secondary outcomes include the change from baseline of mean weekly CSBMs during the follow-up period, mean weekly spontaneous bowel movements (SBMs), overall CSBM response rate, scores on Bristol Stool Form Scale (BSFS), straining level, Patient Assessment of Constipation Symptoms (PAC-SYM), Patient Assessment of Constipation Quality of life questionnaire (PAC-QOL), and Brief Psychiatric Rating Scale (BPRS). Adverse events and medicine use will be recorded as well. DISCUSSION: The study is designed based on a rigorous methodology to evaluate the efficacy and safety of EA for antipsychotic-related constipation. The finding will be published in peer-reviewed journals as reliable evidence. TRIAL REGISTRATION: ClinicalTrials.gov ChiCTR2000032582. Registered May 3, 2020, with the Chinese Clinical Trial Registry.

Acupuncture for the treatment of diarrheal-predominant irritable bowel syndrome: study protocol for a pilot randomized controlled trial.

BACKGROUND: Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal diseases. Although acupuncture has become a common alternative therapy for IBS, there is insufficient evidence for its effectiveness. This study was designed to assess the efficacy and feasibility of acupuncture in the treatment of IBS. METHODS/DESIGN: This is a multicenter randomized controlled clinical trial. According to the ratio of 1:1:1, 90 patients with irritable bowel syndrome will be randomly divided into specific acupoints (SA) group, non-specific acupoints (NSA) group, and non-acupoints (NA) group. All patients will be treated with acupuncture 12 times within 4 weeks and followed up for 8 weeks. The primary outcome is the response rate, the percentage of patients whose average value of worst abdominal pain is 30% better and the days of loose stool is 50% less than the baseline, at week 4 after randomization. The secondary outcomes include the response rates at other time points, IBS Symptom Severity Scale (IBS-SSS), Patient Health Questionnaire-9 depression scale (PHQ-9), IBS-Quality of Life scale (IBS-QOL), IBS Adequate Relief (IBS-AR), Abdominal Pain Score, Abdominal Bloating Score, Bristol Stool Score (BBS), blinding assessment, and credibility evaluation. Adverse events will be monitored and recorded during the trial. TRIAL REGISTRATION: Chictr.org.cn ChiCTR2000030670. Registered on 9 March 2020.

Electroacupuncture ameliorates intestinal inflammation by activating α7nAChR-mediated JAK2/STAT3 signaling pathway in postoperative ileus.

Inflammatory cytokines produced by muscularis macrophages largely contribute to the pathological signs of postoperative ileus (POI). Electroacupuncture (EA) can suppress inflammation, mainly or partly via activation of vagal efferent. The goal of this study was to investigate the mechanisms by which EA stimulation at an hindlimb region ameliorates inflammation in POI. Methods: Intestinal motility and inflammation were examined after 24 h after intestinal manipulation (IM)-induced POI in mice. Local immune response in the intestinal muscularis, expression of macrophages, α7 nicotinic acetylcholine receptor (α7nAChR), Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) were determined by flow cytometry, Western Blot, qPCR and immunofluorescence. The effects of α7nAChR antagonists (methyllycaconitine and α-bungarotoxin) and JAK2/STAT3 inhibitors (AG490 and WP1066) were also administered in a subset of mice prior to EA. In the parasympathetic pathways, intestinal motility and inflammation were determined after cervical vagotomy and sub-diaphragmatic vagotomy. The expression of gamma absorptiometry aminobutyric acid (GABAA) receptor in dorsal motor nucleus of vagal (DMV) cholinergic neurons was assessed by immunofluorescence and the response to DMV microinjection of bicuculine (antagonist of GABAA receptor) or muscimol (agonist of GABAA receptor) were assessed. Results: EA suppressed intestinal inflammation and promoted gastrointestinal motility. Mechanistically, EA activated the α7nAChR-mediated JAK2/STAT3 signaling pathway in macrophages which reduced the production of inflammatory cytokines. Furthermore, we also demonstrated that hindlimb region stimulation drove vagal efferent output by inhibiting the expression of GABAA receptor in DMV to ameliorate inflammation. Conclusions: The present study revealed that EA of hindlimb regions inhibited the expression of GABAA receptor in DMV neurons, whose excited vagal nerve, in turn suppressed IM-induced inflammation via activation of α7nAChR-mediated JAK2/STAT3 signaling pathway.

The Management of Sciatica by Acupuncture: An Expert Consensus Using the Improved Delphi Survey.

OBJECTIVE: Acupuncture therapy is an effective non-drug therapy for sciatica, but it has not yet formed an effective treatment strategy and recommendations. Our objective was to establish an expert consensus on acupuncture treatment of sciatica for clinical guidance based on the improved Delphi survey. METHODS: A group of 80 clinical specialists was invited to participate in two rounds of semi-open clinical issue investigation. At the same time, the PubMed, Embase, and Cochrane Library databases were searched for systematic reviews on acupuncture treatment of sciatica, and the quality of evidence was evaluated. Then the three-round Delphi survey was undertaken with 30 experts based on the clinical issue investigation and systematic reviews. RESULTS: In round 1 of the Delphi survey, the experts evaluated 17 items identified from the results of the clinical investigation and literature review. The criterion for achieving consensus was a threshold of 80% agreement. After the three-round Delphi survey, 16 items (94.12%) achieved consensus, including 5 domains: the principle of acupuncture treatment for sciatica; the "dose" of acupuncture; the clinical effects of acupuncture; the adverse effects, and others. CONCLUSION: This Delphi survey achieved an expert consensus on key items in the management of sciatica for acupuncture, which provides the current opinions in China. We trust that these treatment recommendations may facilitate their implementation in the future.

Acupuncture for persistent atrial fibrillation after catheter ablation: study protocol for a pilot randomized controlled trial.

BACKGROUND: Atrial fibrillation (AF) is a common arrhythmia, which is closely related to cardiovascular morbidity and mortality. Although acupuncture is used in the treatment of AF, the evidence is insufficient. The objective of this pilot trial is to evaluate the feasibility, preliminary efficacy, and safety of acupuncture in reducing AF burden for persistent AF after catheter ablation (CA). METHODS AND DESIGN: This will be a multi-center, 3-arm, pilot randomized controlled trial in China. Sixty patients in total will be randomly assigned to the specific acupoints group, the non-specific acupoints group, or the non-acupoints group in a 1:1:1 ratio. The whole study period is 6 months, including a 3-month treatment period and a 3-month follow-up period. All patients will receive 18 sessions of acupuncture over 12 weeks after CA and appropriate post-ablation routine treatment. The primary outcome is AF burden at 6 months after CA measured by electrocardiography patch that can carry out a 7-day continuous ambulatory electrocardiographic monitoring. The secondary outcomes include AF burden at 3 months after CA, recurrence of AF, quality of life, etc. The adverse events will also be recorded. DISCUSSION: This pilot study will contribute to evaluating the feasibility, preliminary efficacy, and safety of acupuncture in reducing AF burden for persistent AF after CA. The results will be used for the sample size calculation of a subsequent large-scale trial. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2000030576 . Registered on 7 March 2020.

Efficacy of acupuncture for sciatica: study protocol for a randomized controlled pilot trial.

BACKGROUND: Acupuncture is widely used for pain diseases while evidence of its efficacy for sciatica is insufficient. We aim to explore the feasibility and efficacy of acupuncture with different acupoint selecting strategies for sciatica induced by lumbar disc herniation. METHODS: This is a multicenter, three-arm, patient-assessor-blinded randomized controlled pilot trial. Ninety patients will be assigned randomly into 3 groups including disease-affected meridians (DAM) group, non-affected meridians (NAM) group, and sham acupuncture (SA) group in a 1:1:1 ratio. The trial involves a 4-week treatment along with follow-up for 22 weeks. The primary outcome is the change of leg pain intensity measured by the visual analogue scale (VAS) from baseline to week 4 after randomization. Secondary outcomes include functional status, back pain intensity, and quality of life. Adverse events will also be recorded. DISCUSSION: The results will inspire the optimal acupuncture strategy for sciatica and help establish a better design as well as power calculation for a full-scale study. TRIAL REGISTRATION: ChiCTR2000030680 (Chinese Clinical Trial Registry, http://www.chictr.org.cn , registered on 9 March 2020).

Acupuncture for Psychological Disorders Caused by Chronic Pain: A Review and Future Directions.

Accumulating evidence supports an association between chronic pain and psychological disorders, a connection that seems to be bidirectional. Treating both the pain and psychological conditions together is essential for effective treatment outcomes. Acupuncture is a somatosensory-guided mind-body therapy that can tackle the multidimensional nature of pain with fewer or no serious adverse effects. In this review, we discuss the use of acupuncture in some conditions with a high incidence of psychological disorders caused by chronic pain: headache, musculoskeletal pain, low back pain, and cancer pain, focusing on the effect and potential mechanisms of acupuncture. Overall clinical studies indicated that acupuncture might effectively contribute to management of psychological disorders caused by chronic pain. Mechanistic studies showed that acupuncture significantly alleviated such psychological disorders by regulating the activity of amygdala and insula, and regulating functional connectivity of insular and limbic regions/medial prefrontal cortex in humans and the corresponding animal models. In addition, 5-HT in the dorsal raphe nucleus, opioid receptors in the cingulate cortex, and plasma met-enkephalin are involved in acupuncture relief of pain and psychological symptoms. Substantial evidences from animal and human research support a beneficial effect of acupuncture in psychological disorders caused by chronic pain.

Methylated Histidines Alter Tautomeric Preferences that Influence the Rates of Cu Nitrite Reductase Catalysis in Designed Peptides.

Copper proteins have the capacity to serve as both redox active catalysts and purely electron transfer centers. A longstanding question in this field is how the function of histidine ligated Cu centers are modulated by δ vs ε-nitrogen ligation of the imidazole. Evaluating the impact of these coordination modes on structure and function by comparative analysis of deposited crystal structures is confounded by factors such as differing protein folds and disparate secondary coordination spheres that make direct comparison of these isomers difficult. Here, we present a series of de novo designed proteins using the noncanonical amino acids 1-methyl-histidine and 3-methyl-histidine to create Cu nitrite reductases where δ- or ε-nitrogen ligation is enforced by the opposite nitrogen's methylation as a means of directly comparing these two ligation states in the same protein fold. We find that ε-nitrogen ligation allows for a better nitrite reduction catalyst, displaying 2 orders of magnitude higher activity than the δ-nitrogen ligated construct. Methylation of the δ nitrogen, combined with a secondary sphere mutation we have previously published, has produced a new record for efficiency within a homogeneous aqueous system, improving by 1 order of magnitude the previously published most efficient construct. Furthermore, we have measured Michaelis-Menten kinetics on these highly active constructs, revealing that the remaining barriers to matching the catalytic efficiency ( kcat/ KM) of native Cu nitrite reductase involve both substrate binding ( KM) and catalysis ( kcat).

Oxidative Post-translational Modifications Accelerate Proteolytic Degradation of Calprotectin.

Oxidative post-translational modifications affect the structure and function of many biomolecules. Herein we examine the biophysical and functional consequences of oxidative post-translational modifications to human calprotectin (CP, S100A8/S100A9 oligomer, MRP8/MRP14 oligomer, calgranulins A/B oligomer). This abundant metal-sequestering protein contributes to innate immunity by starving invading microbial pathogens of transition metal nutrients in the extracellular space. It also participates in the inflammatory response. Despite many decades of study, little is known about the fate of CP at sites of infection and inflammation. We present compelling evidence for methionine oxidation of CP in vivo, supported by using 15N-labeled CP-Ser (S100A8(C42S)/S100A9(C3S)) to monitor for adventitious oxidation following human sample collection. To elucidate the biochemical and functional consequences of oxidative post-translational modifications, we examine recombinant CP-Ser with methionine sulfoxide modifications generated by exposing the protein to hydrogen peroxide. These oxidized species coordinate transition metal ions and exert antibacterial activity. Nevertheless, oxidation of M81 in the S100A9 subunit disrupts Ca(II)-induced tetramerization and, in the absence of a transition metal ion bound at the His6 site, accelerates proteolytic degradation of CP. We demonstrate that native CP, which contains one Cys residue in each full-length subunit, forms disulfide bonds within and between S100A8/S100A9 heterodimers when exposed to hydrogen peroxide. Remarkably, disulfide bond formation accelerates proteolytic degradation of CP. We propose a new extension to the working model for extracellular CP where post-translational oxidation by reactive oxygen species generated during the neutrophil oxidative burst modulates its lifetime in the extracellular space.

Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity.

Protein design is a useful strategy to interrogate the protein structure-function relationship. We demonstrate using a highly modular 3-stranded coiled coil (TRI-peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H2 O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75-fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three-coordinate CuI in a site, which tends toward two-coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal-center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.

Histidine Orientation Modulates the Structure and Dynamics of a de Novo Metalloenzyme Active Site.

The ultrafast dynamics of a de novo metalloenzyme active site is monitored using two-dimensional infrared spectroscopy. The homotrimer of parallel, coiled coil α-helices contains a His3-Cu(I) metal site where CO is bound and serves as a vibrational probe of the hydrophobic interior of the self-assembled complex. The ultrafast spectral dynamics of Cu-CO reveals unprecedented ultrafast (2 ps) nonequilibrium structural rearrangements launched by vibrational excitation of CO. This initial rapid phase is followed by much slower ∼40 ps vibrational relaxation typical of metal-CO vibrations in natural proteins. To identify the hidden coupled coordinate, small molecule analogues and the full peptide were studied by QM and QM/MM calculations, respectively. The calculations show that variation of the histidines' dihedral angles in coordinating Cu controls the coupling between the CO stretch and the Cu-C-O bending coordinates. Analysis of different optimized structures with significantly different electrostatic field magnitudes at the CO ligand site indicates that the origin of the stretch-bend coupling is not directly due to through-space electrostatics. Instead, the large, ∼3.6 D dipole moments of the histidine side chains effectively transduce the electrostatic environment to the local metal coordination orientation. The sensitivity of the first coordination sphere to the protein electrostatics and its role in altering the potential energy surface of the bound ligands suggests that long-range electrostatics can be leveraged to fine-tune function through enzyme design.

Pulse electron paramagnetic resonance studies of the interaction of methanol with the S2 state of the Mn4O5Ca cluster of photosystem II.

The binding of the substrate analogue methanol to the catalytic Mn4CaO5 cluster of the water-oxidizing enzyme photosystem II is known to alter the electronic structure properties of the oxygen-evolving complex without retarding O2-evolution under steady-state illumination conditions. We report the binding mode of (13)C-labeled methanol determined using 9.4 GHz (X-band) hyperfine sublevel-correlation (HYSCORE) and 34 GHz (Q-band) electron spin-echo electron nuclear double resonance (ESE-ENDOR) spectroscopies. These results are compared to analogous experiments on a mixed-valence Mn(III)Mn(IV) complex (2-OH-3,5-Cl2-salpn)2Mn(III)Mn(IV) (salpn = N,N'-bis(3,5-dichlorosalicylidene)-1,3-diamino-2-hydroxypropane) in which methanol ligates to the Mn(III) ion ( Larson et al. (1992) J. Am. Chem. Soc. , 114 , 6263 ). In the mixed-valence Mn(III,IV) complex, the hyperfine coupling to the (13)C of the bound methanol (Aiso = 0.65 MHz, T = 1.25 MHz) is appreciably larger than that observed for (13)C methanol associated with the Mn4CaO5 cluster poised in the S2 state, where only a weak dipolar hyperfine interaction (Aiso = 0.05 MHz, T = 0.27 MHz) is observed. An evaluation of the (13)C hyperfine interaction using the X-ray structure coordinates of the Mn4CaO5 cluster indicates that methanol does not bind as a terminal ligand to any of the manganese ions in the oxygen-evolving complex. We favor methanol binding in place of a water ligand to the Ca(2+) in the Mn4CaO5 cluster or in place of one of the waters that form hydrogen bonds with the oxygen bridges of the cluster.

De novo-designed metallopeptides with type 2 copper centers: modulation of reduction potentials and nitrite reductase activities.

Enzymatic reactions involving redox processes are highly sensitive to the local electrostatic environment. Despite considerable effort, the complex interactions among different influential factors in native proteins impede progress toward complete understanding of the structure-function relationship. Of particular interest is the type 2 copper center Cu(His)3, which may act as an electron transfer center in peptidylglycine α-hydroxylating monooxygenase (PHM) or a catalytic center in copper nitrite reductase (CuNiR). A de novo design strategy is used to probe the effect of modifying charged amino acid residues around, but not directly bound to, a Cu(His)3 center embedded in three-stranded coiled coils (TRI-H)3 [TRI-H = Ac-G WKALEEK LKALEEK LKALEEK HKALEEK G-NH2]. Specifically, the peptide TRI-EH (=TRI-HK22E) alters an important lysine to glutamate just above the copper binding center. With a series of TRI-EH peptides mutated below the metal center, we use a variety of spectroscopies (EPR, UV-vis, XAS) to show a direct impact on the protonation equilibria, copper binding affinities, reduction potentials, and nitrite reductase activities of these copper-peptide complexes. The potentials at a specific pH vary by 100 mV, and the nitrite reductase activities range over a factor of 4 in rates. We also observe that the affinities, potentials, and catalytic activities are strongly influenced by the pH conditions (pH 5.8-7.4). In general, Cu(II) affinities for the peptides are diminished at low pH values. The interplay among these factors can lead to a 200 mV shift in reduction potential across these peptides, which is determined by the pH-dependent affinities of copper in both oxidation states. This study illustrates the strength of de novo protein design in elucidating the influence of ionizable residues on a particular redox system, an important step toward understanding the factors that govern the properties of this metalloenzyme with a goal of eventually improving the catalytic activity.

Designing a functional type 2 copper center that has nitrite reductase activity within α-helical coiled coils.

One of the ultimate objectives of de novo protein design is to realize systems capable of catalyzing redox reactions on substrates. This goal is challenging as redox-active proteins require design considerations for both the reduced and oxidized states of the protein. In this paper, we describe the spectroscopic characterization and catalytic activity of a de novo designed metallopeptide Cu(I/II)(TRIL23H)(3)(+/2+), where Cu(I/II) is embeded in α-helical coiled coils, as a model for the Cu(T2) center of copper nitrite reductase. In Cu(I/II)(TRIL23H)(3)(+/2+), Cu(I) is coordinated to three histidines, as indicated by X-ray absorption data, and Cu(II) to three histidines and one or two water molecules. Both ions are bound in the interior of the three-stranded coiled coils with affinities that range from nano- to micromolar [Cu(II)], and picomolar [Cu(I)]. The Cu(His)(3) active site is characterized in both oxidation states, revealing similarities to the Cu(T2) site in the natural enzyme. The species Cu(II)(TRIL23H)(3)(2+) in aqueous solution can be reduced to Cu(I)(TRIL23H)(3)(+) using ascorbate, and reoxidized by nitrite with production of nitric oxide. At pH 5.8, with an excess of both the reductant (ascorbate) and the substrate (nitrite), the copper peptide Cu(II)(TRIL23H)(3)(2+) acts as a catalyst for the reduction of nitrite with at least five turnovers and no loss of catalytic efficiency after 3.7 h. The catalytic activity, which is first order in the concentration of the peptide, also shows a pH dependence that is described and discussed.