Assessment of the potential value of plasma Torque Teno virus DNA load monitoring to predict cytomegalovirus DNAemia in patients with hematological malignancies treated with small molecule inhibitors: A proof-of-concept study.

It is unknown whether Torque Teno virus (TTV) DNA load monitoring could anticipate the development of infectious events in hematological patients undergoing treatment with small molecular targeting agents. We characterized the kinetics of plasma TTV DNA in patients treated with ibrutinib or ruxolitinib and assessed whether TTV DNA load monitoring could predict the occurrence of Cytomegalovirus (CMV) DNAemia or the magnitude of CMV-specific T-cell responses. Multicenter, retrospective, observational study, recruiting 20 patients treated with ibrutinib and 21 with ruxolitinib. Plasma TTV and CMV DNA loads were quantified by real-time PCR at baseline and days +15, +30, +45, +60, +75, +90, +120, +150, and +180 after treatment inception. Enumeration of CMV-specific interferon-γ (IFN-γ)-producing CD8+ and CD4+ T-cells in whole blood was performed by flow cytometry. Median TTV DNA load in ibrutinib-treated patients increased significantly (p = 0.025) from baseline (median: 5.76 log10 copies/mL) to day +120 (median: 7.83 log10 copies/mL). A moderate inverse correlation (Rho = -0.46; p < 0.001) was found between TTV DNA load and absolute lymphocyte count. In ruxolitinib-treated patients, TTV DNA load quantified at baseline was not significantly different from that measured after treatment inception (p ≥ 0.12). TTV DNA load was not predictive of the subsequent occurrence of CMV DNAemia in either patient group. No correlation was observed between TTV DNA loads and CMV-specific IFN-γ-producing CD8+ and CD4+ T-cell counts in either patient group. The data did not support the hypothesis that TTV DNA load monitoring in hematological patients treated with ibrutinib or ruxolitinib could be useful to predict either the occurrence of CMV DNAemia or the level of CMV-specific T-cell reconstitution; nevertheless, due to the small sample size, further studies involving larger cohorts are warranted to elucidate this issue.

Accuracy and prognostic impact of FDG PET/CT and biopsy in bone marrow assessment of follicular lymphoma at diagnosis: A Nation-Wide cohort study.

BACKGOUND: In the workup of follicular lymphoma (FL), bone marrow biopsy (BMB) assessment is a key component of FLIPI and FLIPI2, the most widely used outcome scores. During the previous decade, several studies explored the role of FDG-PET/CT for detecting nodal and extranodal disease, with only one large study comparing both techniques. METHODS: The aim of our study was to evaluate the diagnostic accuracy and the prognostic impact of both procedures in a retrospective cohort of 299 FL patients with both tests performed at diagnosis. In order to avoid a collinearity bias, FLIPI2 was deconstructed in its founding parameters, and the bone marrow involvement (BMI) parameter separately included as: a positive BMB, a positive PET/CT, the combined "PET/CT and BMB positive" or "PET/CT or BMB positive". These variables were also confronted independently with the POD24 in 233 patients treated with intensive regimens. RESULTS: In the total cohort, bone marrow was involved in 124 and 60 patients by BMB and PET/CT, respectively. In terms of overall survival, age > 60 y.o. and the combined "PET/CT or BMB positive" achieved statistical independence as a prognostic factor. In patients treated with an intensive regimen, only the combined "PET/CT or BMB positive" added prognostic value for a shorter overall survival, when confronted with the POD24. CONCLUSION: Our results show that in FL both BMB and PET/CT should be considered at diagnosis, as their combined assessment provides independent prognostic value in the context of the most widely use clinical scores.

Electric field-induced functional changes in electrode-immobilized mutant species of human cytochrome c.

Post-translational modifications and naturally occurring mutations of cytochrome c have been recognized as a regulatory mechanism to control its biology. In this work, we investigate the effect of such in vivo chemical modifications of human cytochrome c on its redox properties in the adsorbed state onto an electrode. In particular, tyrosines 48 and 97 have been replaced by the non-canonical amino acid p-carboxymethyl-L-phenylalanine (pCMF), thus mimicking tyrosine phosphorylation. Additionally, tyrosine 48 has been replaced by a histidine producing the natural Y48H pathogenic mutant. Thermodynamics and kinetics of the interfacial electron transfer of wild-type cytochrome c and herein produced variants, adsorbed electrostatically under different local interfacial electric fields, were determined by means of variable temperature cyclic film voltammetry. It is shown that non-native cytochrome c variants immobilized under a low interfacial electric field display redox thermodynamics and kinetics similar to those of wild-type cytochrome c. However, upon increasing the strength of the electric field, the redox thermodynamics and kinetics of the modified proteins markedly differ from those of the wild-type species. The mutations promote stabilization of the oxidized form and a significant increase in the activation enthalpy values that can be ascribed to a subtle distortion of the heme cofactor and/or difference of the amino acid rearrangements rather than to a coarse protein structural change. Overall, these results point to a combined effect of the single point mutations at positions 48 and 97 and the strength of electrostatic binding on the regulatory mechanism of mitochondrial membrane activity, when acting as a redox shuttle protein.

Panel Sequencing for Clinically Oriented Variant Screening and Copy Number Detection in Chronic Lymphocytic Leukemia Patients.

According to current guidelines, in chronic lymphocytic leukemia (CLL), only the TP53 molecular status must be evaluated prior to every treatment's initiation. However, additional heterogeneous genetic events are known to confer a proliferative advantage to the tumor clone and are associated with progression and treatment failure in CLL patients. Here, we describe the implementation of a comprehensive targeted sequencing solution that is suitable for routine clinical practice and allows for the detection of the most common somatic single-nucleotide and copy number variants in genes relevant to CLL. We demonstrate that this cost-effective strategy achieves variant detection with high accuracy, specificity, and sensitivity. Furthermore, we identify somatic variants and copy number variations in genes with prognostic and/or predictive value, according to the most recent literature, and the tool provides evidence about subclonal events. This next-generation sequencing (NGS) capture-based target assay is an improvement on current approaches in defining molecular prognostic and/or predictive variables in CLL patients.

Addition of chemotherapy to nivolumab after PD-1 inhibitor failure as bridge to allogeneic stem cell transplantation in classical Hodgkin's lymphoma: report on three cases and literature review.

The poor prognosis of refractory or relapsed (R/R) classical Hodgkin's lymphoma (cHL) after autologous stem cell transplantation has improved greatly due to the introduction of brentuximab vedotin and PD-1 inhibitors. However, the duration of response achieved with these novel agents is too short. The information about the management of patients after anti-PD-1 therapy failure is very limited in cHL, although chemotherapy alone or combined with PD-1 inhibitors has shown encouraging results. We report three cases of heavily pretreated cHL, refractory to nivolumab monotherapy, successfully rescued with the addition of chemotherapy to nivolumab, as a bridge to allogeneic stem cell transplantation (allo-SCT). All three patients presented poor clinical features such as three to four previous lines including brentuximab vedotin and autologous stem cell transplantation, refractoriness to the last line of therapy previous to nivolumab, and rapid disease progression. Notwithstanding these characteristics and nivolumab failure, they achieved a complete response after the addition of chemotherapy, were consolidated with allo-SCT, and still remain in complete response. There are few studies concerning the combination of PD-1 inhibitors and chemotherapy after nivolumab failure, including one retrospective study and one phase II trial with nivolumab plus bendamustine. Therefore, only few patients are consolidated with allo-SCT. However, there are several ongoing trials investigating new combinations of chemotherapy and PD-1 inhibitors in R/R cHL, as well as in first line. All these data suggest that anti-PD-1 therapy may reprogram the immune system, activating and inhibiting effector and immunosuppressive cells, respectively, leading to overtake of chemorefractoriness. Allo-SCT can increase the immune-related events of patients treated with anti-PD-1 previously, consistent on acute graft-versus-host disease, sinusoidal obstruction syndrome, and noninfectious febrile syndrome. In conclusion, the combination of PD-1 inhibitor and chemotherapy may be a feasible therapy after anti-PD-1 treatment failure as a bridge to allo-SCT.

Structural and functional insights into lysine acetylation of cytochrome c using mimetic point mutants.

Post-translational modifications frequently modulate protein functions. Lysine acetylation in particular plays a key role in interactions between respiratory cytochrome c and its metabolic partners. To date, in vivo acetylation of lysines at positions 8 and 53 has specifically been identified in mammalian cytochrome c, but little is known about the structural basis of acetylation-induced functional changes. Here, we independently replaced these two residues in recombinant human cytochrome c with glutamine to mimic lysine acetylation and then characterized the structure and function of the resulting K8Q and K53Q mutants. We found that the physicochemical features were mostly unchanged in the two acetyl-mimetic mutants, but their thermal stability was significantly altered. NMR chemical shift perturbations of the backbone amide resonances revealed local structural changes, and the thermodynamics and kinetics of electron transfer in mutants immobilized on gold electrodes showed an increase in both protein dynamics and solvent involvement in the redox process. We also observed that the K8Q (but not the K53Q) mutation slightly increased the binding affinity of cytochrome c to its physiological electron donor, cytochrome c1 -which is a component of mitochondrial complex III, or cytochrome bc1 -thus suggesting that Lys8 (but not Lys53) is located in the interaction area. Finally, the K8Q and K53Q mutants exhibited reduced efficiency as electron donors to complex IV, or cytochrome c oxidase.

Central Nervous System Involvement in Epstein-Barr Virus-Related Post-Transplant Lymphoproliferative Disorders after Allogeneic Hematopoietic Stem Cell Transplantation.

Central nervous system (CNS) involvement in Epstein-Barr virus-related post-transplant lymphoproliferative disorders (EBV-PTLDs) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is poorly defined. We analyzed the incidence, clinical and pathological characteristics, and impact on outcomes of EBV-PTLDs with CNS involvement (CNS-PTLDs) in 1009 consecutive adult patients undergoing allo-HSCT at a single-center institution. Four hundred eighty-two patients received matched sibling donor (MSD) transplants, 388 umbilical cord blood transplants (UCBTs), 56 matched unrelated donor (MUD) transplants, and 83 haploidentical transplants. We detected 25 cases of biopsy-proven EBV-PTLDs. Of these, nine patients (36%) had CNS-PTLDs: six after UCBT (67%), one after MSD transplantation (11%), one after MUD transplantation (11%), and one after haploidentical transplantation (11%). The 5-year cumulative incidence risk of CNS-PTLDs was 0.9%. Median time from transplant to CNS-PTLDs was 187 days, and all patients had neurological symptoms at diagnosis. Six out of the nine cases (67%) occurred with systemic involvement, and three cases (33%) had isolated CNS involvement. The most frequent histological subtype was monomorphic EBV-PTLD, and laboratory characteristics were similar to EBV-PTLDs without CNS involvement. We observed statistical differences in the rate of positive EBV DNA detection in plasma between isolated CNS-PTLDs (detection in one out of three, 33%) and the rest of the EBV-PTLDs (100%) (P = .01). Treatment strategies included chemotherapy, radiotherapy, and T cell therapy. However, seven out of nine patients died due to progression of the CNS-PTLDs at a median time of 17 days (range, 8 to 163) from diagnosis. The 5-years overall survival in patients who developed CNS-PTLDs was 22% (95% confidence interval [CI], 7% to 75%) and 5-year treatment-related mortality was 78% (95% CI, 51% to 100%), with no statistically significant differences between CNS-PTLDs and the rest of the EBV-PTLDs. In conclusion, despite advances in EBV monitoring and treatment strategies, CNS-PTLDs remain an uncommon but serious complication after allo-HSCT, with very poor prognosis.

Active Role of the Buffer in the Proton-Coupled Electron Transfer of Immobilized Iron Porphyrins.

Evaluation of the proton-coupled electron transfer thermodynamics of immobilized hemin is challenging due to the disparity of its electrochemical titration curves reported in the literature. Deviations from the one-electron, one-proton transfer at circumneutral pHs have been commonly ascribed to either the formation of dimeric species or the ionization of a second iron-bound water molecule. Herein, however, we report on non-idealities in the more acidic region, whose onset and extent vary with the nature and concentration of the commonly used phosphate and acetate buffers. It is shown that these deviations originate in the ligand-exchange binding between the oxidized aquo-hemin complex and the anionic components of the buffer, so that they are restricted to the pH interval where these forms coexist. A stepwise approach was developed to quantify unambiguously the apparent and intrinsic binding equilibrium constants. The apparent binding equilibrium constant exhibits a peak-shaped pH dependence, whose maximum is located at approximately the midpoint between the pKa of the iron-bound water and the first pKa of the buffer, and its magnitude is greater for the phosphate than for the acetate buffer. But strikingly, the opposite trend was found for the magnitude of the intrinsic binding equilibrium constants determined from the apparent ones, due to the different relative locations of the phosphoric and acetic pKa values with respect to that of the oxidized aquo-hemin. To probe the role of the heme propionic residues, a similar study was carried out with a propionic-free iron porphyrin containing eight ethyl residues. These substituents decrease the acidity of the iron-bound water, strengthen the iron(III)-acetate binding, weaken the iron(III)-dihydrogen phosphate binding, and enable the binding between iron(III) and monohydrogen phosphate, which was hampered in hemin by the presence of the negatively charged propionate residues. Overall, this work provides a more complete speciation of immobilized iron porphyrins under acidic conditions than previously considered, showing the substitutional lability of the aqua ligand in the oxidized state of the iron center and the reluctance of its hydroxyl counterpart to anion exchange. Knowledge of these redox- and pH-dependent bindings with the buffer components is crucial for a rigorous quantification of the proton-coupled electron transfer and the electrocatalytic activity of iron porphyrins.

Physical contact between cytochrome c1 and cytochrome c increases the driving force for electron transfer.

In oxidative phosphorylation, the transfer of electrons from reduced cofactors to molecular oxygen via the electron transport chain (ETC) sustains the electrochemical transmembrane potential needed for ATP synthesis. A key component of the ETC is complex III (CIII, cytochrome bc1), which transfers electrons from reduced ubiquinone to soluble cytochrome c (Cc) coupled to proton translocation into the mitochondrial intermembrane space. One electron from every two donated by hydroquinone at site P is transferred to Cc via the Rieske-cytochrome c1 (Cc1) pathway. According to recent structural analyses of CIII and its transitory complex with Cc, the interaction between the Rieske subunit and Cc1 switches intermittently during CIII activity. However, the electrochemical properties of Cc1 and their function as a wire between Rieske and Cc are rather unexplored. Here, temperature variable cyclic voltammetry provides novel data on the thermodynamics and kinetics of interfacial electron transfer of immobilized Cc1. Findings reveal that Cc1 displays two channels for electron exchange, with a remarkably fast heterogeneous electron transfer rate. Furthermore, the electrochemical properties are strongly modulated by the binding mode of the protein. Additionally, we show that electron transfer from Cc1 to Cc is thermodynamically favored in the immobilized Cc1-Cc complex. Nuclear Magnetic Resonance, HADDOCK, and Surface Plasmon Resonance experiments provide further structural and functional data of the Cc1-Cc complex. Our data supports the Rieske-Cc1-Cc pathway acting as a unilateral switch thyristor in which redox potential modulation through protein-protein contacts are complemented with the relay-like Rieske behavior.

RELINF: prospective epidemiological registry of lymphoid neoplasms in Spain. A project from the GELTAMO group.

Lymphomas are a large, heterogeneous group of neoplasms with well-defined characteristics, and this heterogeneity highlights the importance of epidemiological data. Knowledge of local epidemiology is essential to optimise resources, design clinical trials, and identify minority entities. Given there are few published epidemiological data on lymphoma in Spain, the Spanish Lymphoma and Autologous Bone Marrow Transplant Group created the RELINF project. The aim of this project is to determine the frequencies and distribution of lymphoid neoplasms in Spain and to analyse survival. We developed an online platform for the prospective collection of data on newly diagnosed cases of lymphoma in Spain between January 2014 and July 2018; 11,400 patients were registered. Diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL) were the most frequent lymphomas in our series. Marginal B cell lymphoma frequency was higher than that reported in other studies, representing more than 11% of mature B cell lymphomas. Peripheral T cell lymphoma not otherwise specified (PTCL-NOS) was the most common subtype of T cell lymphoma, and NK/T cell lymphomas were more frequent than expected (5.4% of total). Hodgkin's lymphoma accounted for 12% of lymphoproliferative syndromes. Overall survival was greater than 90% at 2 years for indolent B cell lymphomas, and approximately 60% for DLBCL, somewhat lower than that previously reported. Survival was poor for PTCL-NOS and angioimmunoblastic T cell lymphoma, as expected; however, it was somewhat better than that in other studies for anaplastic large cell anaplastic lymphoma kinase lymphomas. This is the first prospective registry to report the frequencies, distribution, and survival of lymphomas in Spain. The frequencies and survival data we report here are globally consistent with that reported in other Western countries. These updated frequencies and survival statistics are necessary for developing appropriate management strategies for neoplasias in the Spanish population.

Partial T Cell-Depleted Peripheral Blood Stem Cell Transplantation from HLA-Identical Sibling Donors for Patients with Severe Aplastic Anemia.

We analyzed the outcomes of 26 consecutive patients with acquired severe aplastic anemia (SAA) undergoing peripheral blood stem cell transplantation (PBSCT) with partial ex vivo T cell depletion with a targeted T cell dose from HLA-identical sibling donors. The median patient age was 37 years (range, 3 to 63 years). Four patients with uncontrolled pneumonia at the time of transplantation died, on days +1, +2, +21, and +26. All evaluable patients engrafted, with a median time to neutrophil recovery of 11 days (range, 10 to 14 days) and a median time to platelet recovery of 19 days (range, 8 to 53 days). Two patients had transient grade I acute graft-versus-host disease (GVHD) with skin involvement, but no patients developed grade II-IV acute GVHD. Two patients had mild skin chronic GVHD, and 1 patient had moderate chronic GVHD with ocular involvement. No relapse was observed after a median follow-up of 114 months (range, 4 to 233 months). The overall cumulative incidence of TRM at 10 years was 19%, whereas it was 5% for those with a Karnofsky Performance Status (KPS) score >60 at the time of transplantation. Disease-free survival, overall survival, and GVHD and relapse-free survival at 10 years were 81%, 81%, and 80%, respectively, for all patients and 95%, 95%, and 90%, respectively, for patients with a KPS score >60 at transplantation. Our data indicate that PBSCT with partial ex vivo T cell-depleted targeted cell dose grafts from an HLA-identical sibling donor is a feasible, safe, and effective approach to reduce GVHD and cure patients with SAA.

Post-transplant lymphoproliferative disorders after solid organ and hematopoietic stem cell transplantation.

Post-transplant lymphoproliferative disorders (PTLD) are a rare complication after both solid organ (SOT) and allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this single center retrospective study, we compared clinical, biological, and histological features, and outcomes of PTLD after both types of transplant. We identified 82 PTLD (61 after SOT and 21 after allo-HSCT). The presence of B symptoms, Waldeyer ring, spleen, central nervous system, and liver involvement, and advanced Ann-Arbor stage were more frequent in allo-HSCT recipients. PTLD had an earlier onset in allo-HSCT than in SOT cohort (4 vs. 64 months, p < .0001). PTLD was EBV-positive in 100% of allo-HSCT, in contrast to 47% of SOT (p = .0002). Four years after PTLD diagnosis, median overall survival was 32% (95% CI, 22-48) and 10% (95% CI, 2-49) in SOT and allo-HSCT recipients, respectively (p = .002). In conclusion, the clinical presentation and the outcome of PTLD varies greatly depending on the type of transplant.

Protein crosslinking improves the thermal resistance of plastocyanin immobilized on a modified gold electrode.

Increasing the thermal stability of immobilized proteins is a motivating goal for improving the performance of electrochemical biodevices. In this work, we propose the immobilization of crosslinked plastocyanin from the thermophilic cyanobacterium Phormidium laminosum by simultaneous incubation of a mixture of plastocyanin and the coupling reagents. The thermal stability of the so built covalently immobilized protein films has been assessed by cyclic voltammetry in the 0-90 °C temperature range and has been compared to that of physisorbed films. It is shown that the protein loss along a thermal cycle is significantly reduced in the case of the crosslinked films, whose redox properties remain unaltered along a cyclic heating-cooling thermal scan, and can withstand the contact with 70 °C solutions for four hours. Comparison of thermal unfolding curves obtained by circular dichroism spectroscopy of both free and crosslinked protein confirms the improved thermic resistance of the crosslinked plastocyanin. Notably, the electron transfer thermodynamics of physisorbed and crosslinked plastocyanin films are quite similar, suggesting that the formation of intra- and inter-protein amide bonds do not affect the integrity and functionality of the copper redox centers. UV-Vis absorption and circular dichroism measurements corroborate that protein crosslinking does not alter the coordination geometry of the metal center.

Key Role of the Local Hydrophobicity in the East Patch of Plastocyanins on Their Thermal Stability and Redox Properties.

Understanding the molecular basis of the thermal stability and functionality of redox proteins has important practical applications. Here, we show a distinct thermal dependence of the spectroscopic and electrochemical properties of two plastocyanins from the thermophilic cyanobacterium Phormidium laminosum and their mesophilic counterpart from Synechocystis sp. PCC 6803, despite the similarity of their molecular structures. To explore the origin of these differences, we have mimicked the local hydrophobicity in the east patch of the thermophilic protein by replacing a valine of the mesophilic plastocyanin by isoleucine. Interestingly, the resulting mutant approaches the thermal stability, redox thermodynamics, and dynamic coupling of the flexible site motions of the thermophilic protein, indicating the existence of a close connection between the hydrophobic packing of the east patch region of plastocyanin and the functional control and stability of the oxidized and reduced forms of the protein.

Considering Bone Marrow Blasts From Nonerythroid Cellularity Improves the Prognostic Evaluation of Myelodysplastic Syndromes.

PURPOSE: WHO classification of myeloid malignancies is based mainly on the percentage of bone marrow (BM) blasts. This is considered from total nucleated cells (TNCs), unless there is erythroid-hyperplasia (erythroblasts ≥ 50%), calculated from nonerythroid cells (NECs). In these instances, when BM blasts are ≥ 20%, the disorder is classified as erythroleukemia, and when BM blasts are < 20%, as myelodysplastic syndrome (MDS). In the latter, the percentage of blasts is considered from TNCs. PATIENTS AND METHODS: We assessed the percentage of BM blasts from TNCs and NECs in 3,692 patients with MDS from the Grupo Español de Síndromes Mielodisplásicos, 465 patients with erythroid hyperplasia (MDS-E) and 3,227 patients without erythroid hyperplasia. We evaluated the relevance of both quantifications on classification and prognostication. RESULTS: By enumerating blasts systematically from NECs, 22% of patients with MDS-E and 12% with MDS from the whole series diagnosed within WHO categories with < 5% BM blasts, were reclassified into higher-risk categories and showed a poorer overall survival than did those who remained in initial categories (P = .006 and P = .001, respectively). Following WHO recommendations, refractory anemia with excess blasts (RAEB)-2 diagnosis is not possible in MDS-E, as patients with 10% to < 20% BM blasts from TNCs fulfill erythroleukemia criteria; however, by considering blasts from NECs, 72 patients were recoded as RAEB-2 and showed an inferior overall survival than did patients with RAEB-1 without erythroid hyperplasia. Recalculating the International Prognostic Scoring System by enumerating blasts from NECs in MDS-E and in the overall MDS population reclassified approximately 9% of lower-risk patients into higher-risk categories, which indicated the survival expected for higher-risk patients. CONCLUSION: Regardless of the presence of erythroid hyperplasia, calculating the percentage of BM blasts from NECs improves prognostic assessment of MDS. This fact should be considered in future WHO classification reviews.

Interprotein Coupling Enhances the Electrocatalytic Efficiency of Tobacco Peroxidase Immobilized at a Graphite Electrode.

Covalent immobilization of enzymes at electrodes via amide bond formation is usually carried out by a two-step protocol, in which surface carboxylic groups are first activated with the corresponding cross-coupling reagents and then reacted with protein amine groups. Herein, it is shown that a modification of the above protocol, involving the simultaneous incubation of tobacco peroxidase and the pyrolytic graphite electrode with the cross-coupling reagents produces higher and more stable electrocatalytic currents than those obtained with either physically adsorbed enzymes or covalently immobilized enzymes according to the usual immobilization protocol. The remarkably improved electrocatalytic properties of the present peroxidase biosensor that operates in the 0.3 V ≤ E ≤ 0.8 V (vs SHE) potential range can be attributed to both an efficient electronic coupling between tobacco peroxidase and graphite and to the formation of intra- and intermolecular amide bonds that stabilize the protein structure and improve the percentage of anchoring groups that provide an adequate orientation for electron exchange with the electrode. The optimized tobacco peroxidase sensor exhibits a working concentration range of 10-900 µM, a sensitivity of 0.08 A M(-1) cm(-2) (RSD 0.05), a detection limit of 2 µM (RSD 0.09), and a good long-term stability, as long as it operates at low temperature. These parameter values are among the best reported so far for a peroxidase biosensor operating under simple direct electron transfer conditions.