Spanish-language cognitive screening tests: a critical review.

INTRODUCTION: Dementia is a chronic, degenerative disease with a strong impact on families and health systems. The instruments currently in use for measuring cognitive impairment have different psychometric characteristics in terms of application time, cut-off point, reliability, and validity. The objective of this review is to describe the characteristics of the validated, Spanish-language versions of the Mini-Cog, Clock-Drawing Test, and Mini-Mental State Examination scales for cognitive impairment screening. DEVELOPMENT: We performed a three-stage literature search of articles published on Medline since 1953. We selected articles on validated, Spanish-language versions of the scales that included data on reliability, validity, sensitivity, and specificity. CONCLUSIONS: The 3 screening tools assessed in this article provide support for primary care professionals. Timely identification of mild cognitive impairment and dementia is crucial for the prognosis of these patients.

Escalas de tamizaje cognitivo en habla hispana: una revisión crítica / Spanish-language screening scales: A critical review

Introducción: La demencia es una enfermedad crónica degenerativa de alto impacto para las familias y los sistemas de salud. Los instrumentos de medición del deterioro cognitivo que se utilizan actualmente tienen características psicométricas diferentes en cuanto a tiempo de aplicación, punto de corte, confiabilidad y validez. El objetivo de la presente revisión fue describir las características de las escalas Mini Cog, Prueba del reloj y Mini- Mental para tamizaje de deterioro cognitivo validadas al idioma español. Desarrollo: La búsqueda bibliográfica se realizó en 3 etapas mediante la base de datos Medline a partir del año 1953. Se realizó una selección de publicaciones validadas al español que incluyeran la confiabilidad, validez, sensibilidad y especificidad de las escalas. Conclusiones: Las 3 herramientas de tamizaje descritas en este artículo proporcionan un apoyo para el personal de salud. La detección oportuna es crucial para el pronóstico de las personas que viven con deterioro cognitivo leve o demencia. (AU)

Introduction: Dementia is a chronic, degenerative disease with a strong impact on families and health systems. The instruments currently in use for measuring cognitive impairment have different psychometric characteristics in terms of application time, cut-off point, reliability, and validity. The objective of this review is to describe the characteristics of the validated, Spanish-language versions of the Mini-Cog, Clock-Drawing Test, and Mini–Mental State Examination scales for cognitive impairment screening. Development: We performed a three-stage literature search of articles published on Medline since 1953. We selected articles on validated, Spanish-language versions of the scales that included data on reliability, validity, sensitivity, and specificity. Conclusions: The 3 screening tools assessed in this article provide support for primary care professionals. Timely identification of mild cognitive impairment and dementia is crucial for the prognosis of these patients. (AU)

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in nonhuman primates.

Dopaminergic neuronal cell death, associated with intracellular α-synuclein (α-syn)-rich protein aggregates [termed "Lewy bodies" (LBs)], is a well-established characteristic of Parkinson's disease (PD). Much evidence, accumulated from multiple experimental models, has suggested that α-syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here, we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct α-syn pathogenic structures derived from patients with PD. Unexpectedly, our results show that, in nonhuman primates, a small amount of singular α-syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD, as multiple causes can induce a similar outcome regarding dopaminergic neurodegeneration.

Effects of topical applications of porcine acellular urinary bladder matrix and Centella asiatica extract on oral wound healing in a rat model.

OBJECTIVES: To evaluate the effects of topical applications of porcine acellular urinary bladder matrix (AUBM) and Centella asiatica extract (CAE) on the healing of tongue wounds in a rat model. MATERIALS AND METHODS: Wounds were made in the tongue using a punch tool in 64 male Sprague-Dawley rats, randomized into four groups (n = 16 per group): group 1 (control), group 2 (CAE), group 3 (AUBM mixed with orabase), and group 4 (orabase). No product was applied in group 1 and groups 2-4 received three daily topical applications. The animals were weighed on day 0 and at the time of euthanasia. Four rats in each group were euthanized at days 2, 7, 14, and 21 and the tongues were processed for: macroscopic morphometric analysis, myeloperoxidase (MPO) and malondialdehyde (MDA) levels, histological wound repair (degree of reepithelialization and inflammation), and CD31 positivity. RESULTS: The animals' weight gain, histological wound repair, and CD31 positivity from greatest to least were: AUBM > CAE > orabase > control. Percentage of tongue occupied by wound, MPO, and MPA levels from least to greatest were: AUBM < CAE < orabase < control, whereby the AUBM group showed significant differences (p ≤ 0.05) in comparison with the other groups on days 2, 7, 14, and 21 for percentage of tongue occupied by wound and MDA and on days 7, 14, and 21 for MPO. CONCLUSIONS: CAE is effective for oral tissue regeneration, while AUBM is an even more potent means of oral mucosa regeneration. CLINICAL RELEVANCE: AUBM may be beneficial to patients with oral wounds; this finding requires further clinical and laboratory investigation.

Bayesian model of disease progression in GNE myopathy.

One Sentence Summary: A Bayesian repeated measures model based on quantitative muscle strength data from a prospective Natural History Study was developed to determine disease progression and design clinical trials for GNE myopathy, a rare and slowly progressive muscle disease. GNE myopathy is a rare muscle disease characterized by slowly progressive weakness and atrophy of skeletal muscles. To address the significant challenges of defining the natural history and designing clinical trials for GNE myopathy, we developed a Bayesian latent variable repeated measures model to determine disease progression. The model is based on longitudinal quantitative muscle strength data collected as part of a prospective Natural History Study. The GNE Myopathy Progression Model provides an understanding of disease progression that would have otherwise required a natural history of unfeasible duration. "Disease age," the model-generated measure of disease progression, highly correlates with a variety of clinical, functional and patient-reported outcomes. With the incorporation of a treatment effect parameter to the GNE Disease Progression Model, we describe a novel GNE Myopathy Disease Modification Analysis that significantly increases power and reduces the number of subjects required to test the effectiveness of novel therapies when compared to more traditional analysis methods. The GNE Myopathy Disease Progression Model and Disease Modification Analysis can be applied to muscle diseases with prospectively collected muscle strength data, and a variety of rare and slowly progressive diseases.

Spanish-language screening scales: A critical review. / Escalas de tamizaje cognitivo en habla hispana: una revisión crítica.

INTRODUCTION: Dementia is a chronic, degenerative disease with a strong impact on families and health systems. The instruments currently in use for measuring cognitive impairment have different psychometric characteristics in terms of application time, cut-off point, reliability, and validity. The objective of this review is to describe the characteristics of the validated, Spanish-language versions of the Mini-Cog, Clock-Drawing Test, and Mini-Mental State Examination scales for cognitive impairment screening. DEVELOPMENT: We performed a three-stage literature search of articles published on Medline since 1953. We selected articles on validated, Spanish-language versions of the scales that included data on reliability, validity, sensitivity, and specificity. CONCLUSIONS: The 3 screening tools assessed in this article provide support for primary care professionals. Timely identification of mild cognitive impairment and dementia is crucial for the prognosis of these patients.

MIF functional polymorphisms (-794 CATT5-8 and -173 G>C) are associated with MIF serum levels, severity and progression in male multiple sclerosis from western Mexican population.

Macrophage migration inhibitory factor (MIF) is a cytokine associated with tissue damage in multiple autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis and psoriatic arthritis. The role of MIF in multiple sclerosis (MS) and the contribution of its polymorphisms are unknown in our population. Therefore, we decided to investigate the genetic association of -794 CATT5-8 (rs5844572) and -173 G>C (rs755622) MIF polymorphisms with MS, clinical variables and MIF serum levels in the population of western Mexico. 230 MS patients diagnosed according to McDonald criteria and 248 control subjects (CS) were recruited for this study, both polymorphisms were genotyped by PCR and PCR-RFLP and MIF serum levels were measured by ELISA kit. Severity and progression of MS were evaluated by EDSS and MSSS scores, respectively. Genotypes carrying the 5 repeats alleles of -794 CATT5-8MIF polymorphism present higher MIF serum levels in comparison with no carriers, and the presence of 5,7 heterozygous genotype contribute to the increase of disease severity and damage progression in MS patients. Notably when we stratified by sex, an effect of risk alleles (7 repeats and -173*C) of both MIF polymorphisms on EDSS and MSSS scores on males was found (p < 0.01). This study suggests that polymorphic alleles of MIF polymorphisms could act as sex-specific disease modifiers that increase the severity and progression of MS in male Mexican-Mestizo western population.

Open-Label Allopregnanolone Treatment of Men with Fragile X-Associated Tremor/Ataxia Syndrome.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting approximately 45% of male and 16% of female carriers of the FMR1 premutation over the age of 50 years. Currently, no effective treatment is available. We performed an open-label intervention study to assess whether allopregnanolone, a neurosteroid promoting regeneration and repair, can improve clinical symptoms, brain activity, and magnetic resonance imaging (MRI) measurements in patients with FXTAS. Six patients underwent weekly intravenous infusions of allopregnanolone (2-6 mg over 30 min) for 12 weeks. All patients completed baseline and follow-up studies, though MRI scans were not collected from 1 patient because of MRI contraindications. The MRI scans from previous visits, along with scans from 8 age-matched male controls, were also included to establish patients' baseline condition as a reference. Functional outcomes included quantitative measurements of tremor and ataxia and neuropsychological evaluations. Brain activity consisted of event-related potential N400 word repetition effect during a semantic memory processing task. Structural MRI outcomes comprised volumes of the hippocampus, amygdala, and fluid-attenuated inversion recovery hyperintensities, and microstructural integrity of the corpus callosum. The results of the study showed that allopregnanolone infusions were well tolerated in all subjects. Before treatment, the patients disclosed impairment in executive function, verbal fluency and learning, and progressive deterioration of all MRI measurements. After treatment, the patients demonstrated improvement in executive functioning, episodic memory and learning, and increased N400 repetition effect amplitude. Although MRI changes were not significant as a group, both improved and deteriorated MRI measurements occurred in individual patients in contrast to uniform deterioration before the treatment. Significant correlations between baseline MRI measurements and changes in neuropsychological test scores indicated the effects of allopregnanolone on improving executive function, learning, and memory for patients with relatively preserved hippocampus and corpus callosum, while reducing psychological symptoms for patients with small hippocampi and amygdalae. The findings show the promise of allopregnanolone in improving cognitive functioning in patients with FXTAS and in partially alleviating some aspects of neurodegeneration. Further studies are needed to verify the efficacy of allopregnanolone for treating FXTAS.

Osteogenic potential of platelet-rich plasma in dental stem-cell cultures.

The purpose of this study was to analyse the potential of platelet-rich plasma (PRP) culture media to induce osteogenic differentiation of periodontal ligament stem cells and dental pulp stem cells compared with four other methods of culture. Both types of cell were collected from 35 healthy patients and cultured in five different media (Dulbecco's modified eagle's medium (DMEM); DMEM and melatonin; DMEM and PRP; DMEM and ascorbic acid 200µmol; DMEM and l-ascorbate 2-phosphate 50µmol). Cells were characterised by flow cytometry. Alizarin Red stain, alkaline phosphatase stain, and the expression of collagen type 1 (Col-1), runt-related transcription factor (RUNX2), osteoprotegerin, and osteopontin (quantified by qRT-PCR) were used to detect the osteogenic profile in each culture. Flow cytometry showed that both types of stem cell were a homogeneous mixture of CD90(+), CD105(+), STRO-1(+), CD34 (-), and CD45 (-) cells. Dental pulp stem cells that were cultured with PRP showed the best osteogenic profile (RUNX2 p=0.0002; osteoprotegerin p=0.001). The group of these stem cells that showed the best osteogenic profile was also cultured with PRP (osteoprotegerin p=0.001). Medium five (with l-ascorbate 2-phosphate 50µmol added) showed an increase in all osteogenic markers for periodontal ligament stem cells after PRP, while the best culture conditions for osteogenic expression of dental pulp stem cells after PRP was in medium four (ascorbic acid 200µmol added). These results suggested that culture in PRP induces osteogenic differentiation of both types of stem cell, modulating molecular pathways to promote bony formation.

25-OH-Vitamin D Is Not Associated with Cognitive Performance among Mexican Community-Dwelling Older Persons.

BACKGROUND: Low cognitive performance has been associated with a wide array of adverse health-related outcomes in elderly populations. Recently, the effect of vitamin D on cognition has been studied; however, its benefits are still controversial. Moreover, most studies have been carried out on North-American and European populations where vitamin D deficiency could represent a greater public-health issue when compared to Latin American ones. OBJECTIVE: To investigate the association between 25-OH-vitamin D and cognitive performance in Mexican community-dwelling elderly. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional study sample of 331 community-dwelling elderly aged 70 and older, participating in the Mexican Study of Nutritional and Psychosocial Markers of Frailty. MEASUREMENTS: Serum 25-OH-vitamin D, cognitive performance as per the Mini-Mental State Examination (MMSE) and the IST (Isaacs Set Test), as well as several elements from the comprehensive geriatric assessment. RESULTS: Mean age of participants was 79.3 years (SD 5.9), 54.1% were women. The mean serum 25-OH-vitamin D level was 59.0 (SD 23.3) nmol/L while mean MMSE score was 22.3 (SD 3.4) and mean IST score was 37.1 (SD 9.1). Although 25-OH-vitamin D levels were lower across all the definitions of low cognitive perfomance, the difference between groups was not statistically significant in any of them. CONCLUSION: No association between 25-OH-vitamin D level and cognitive performance was found in this population of Mexican community-dwelling elderly. Further investigation is required in order to clarify its existence and if so, to delineate its characteristics.

The -383A>C TNFRI polymorphism is associated with soluble levels and clinical activity in rheumatoid arthritis.

Tumor necrosis factor-alpha (TNF-alpha) plays a central role in inflammation, and it has been directly implicated in the pathogenesis of rheumatoid arthritis (RA). TNF-alpha activity is mediated through TNFRI and TNFRII cell surface receptors, which act as physiological attenuators of TNF-alpha activity. We recruited 190 RA patients and 190 healthy subjects (HS) in order to associate the -383A>C TNFRI polymorphism with sTNFRI levels and DAS28 score in RA. In results, sTNFRI levels were higher in RA patients than HS (P = 0.04). The -383A>C TNFRI polymorphism did not show significant differences in both studied groups. However, in the RA group the sTNFRI levels were significantly elevated (P = 0.004) in A/A genotype carriers. In addition, the A/A genotype carriers had the higher DAS28 score than A/C genotype (P = 0.02). These data suggest that -383A>C TNFRI polymorphism is not a susceptibility marker in RA, whereas the increased levels of sTNFRI could reflect the clinical activity in RA patients.

Circulating TNFRI and TNFRII levels correlated with the disease activity score (DAS28) in rheumatoid arthritis.

OBJECTIVE: To measure levels of soluble tumour necrosis factor alpha (TNFalpha) receptor type I (sTNFRI) and type II (sTNFRII) in order to correlate them with C-reactive protein (CRP), rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), and disease activity score (DAS28) in RA patients. METHODS: We recruited 41 RA patients classified according to American College of Rheumatology (ACR) criteria and 38 healthy subjects (HS). sTNFRI and sTNFRII were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Clinical activity in RA patients was evaluated using the Disease Activity Score using 28 joint counts (DAS28). The statistical analysis was realized using SPSS version 10.0. RESULTS: Soluble TNFRI and TNFRII levels were higher in RA patients (p = 0.04 and 0.001, respectively) than HS. Serum levels of sTNFRI correlated with sTNFRII (r = 0.699, p < 0.0001). sTNFRII correlated with DAS28 (r = 0.375, p = 0.017), RF (r = 0.505, p = 0.004), and ESR (r = 0.323, p = 0.042). CONCLUSION: The increased levels of both sTNFRI and sTNFRII suggest a secondary event related to the inflammatory state observed in RA, whereas the correlation of sTNFRII with RF, ESR, and DAS28 reflects the preferential TNFRII shedding induced by TNFalpha. sTNFRII may be useful as an additional inflammatory marker in RA.

Vasculitis leucocitoclástica como primera manifestación de pleuritis tuberculosa / Leukocytoclastic vasculitis as the first manifestation of tuberculous pleuritis

En nuestro país la tuberculosis es aún una enfermedad muy prevalente. La tuberculosis puede comprometer cualquier órgano, uno de ellos es la piel. Este compromiso dérmico, se puede evidenciar por la formación de inmunocomplejos que se depositan en la piel y se manifiestan como vasculitis leucocitoclástica. Se presenta el caso de un paciente de 34 años, con un tiempo de enfermedad de cuatro meses, cuyas manifestaciones clínicas iniciales fueron púrpura palpable en miembros inferiores y poliartralgias, quien recibió antinflamatorios no esteroideos durante un mes, presentando leve mejoría de dichas lesiones; luego de un periodo subclínico reinicia sintomatología con fiebre, astenia y dolor torácico. Se evidenció derrame pleural izquierdo, el cual dio como resultado un exudado mononuclear y adenosin deaminasa elevada. En la biopsia pleural se observó granulomas y se evidenció BK positivo. En la biopsia de piel se evidenció una vasculitis leucocitoclástica. Recibió tratamiento específico esquema I, con evolución clínica favorable a los diez días.

In our country tuberculosis is still a very prevalent disease. Tuberculosis can affect any organ, included the skin. This cutaneous disorder can be evidenced by the formation of immunocomplex that are deposited at the skin and manifested as leukocytoclastic vasculitis. We describe the case of a 34 years old patient, with an illness time of four months, whose initial clinical manifestations were palpable purpura on the lower limbs and polyarthralgia, received non-steroidalanti inflammatory drugs for a month, showing slight improvement from such injury; after a subclinical period its symptoms restarts with fever, fatigue and pain chest. There was evidence of left pleural effusion, which resulted in an mononuclear exudate and elevationa of adenosine deaminase. Pleural biopsy showed granulomas and positive BK. Skin biopsy showed leukocytoclastic vasculitis. The patient received first line antituberculosis drugs with favorable clinical outcome after ten days.

Genotype Ser413/Ser of PAI-2 polymorphism Ser413/Cys is associated with anti-phospholipid syndrome and systemic lupus erythematosus in a familial case: comparison with healthy controls.

BACKGROUND: We describe a family with a 7-year-old proband case diagnosed with systemic lupus erythematosus (SLE) plus secondary anti-phospholipid syndrome (APS) as well as two affected paternal aunts. We compared the frequency of these polymorphisms with healthy controls. OBJECTIVES: To evaluate the mode of inheritance in this familial case of APS and SLE and the possible association of plasminogen activator inhibitor-1 (PAI-1) -675 4G/5G and PAI-2 Ser(413)/Cys polymorphisms. To compare the genotype frequency of these polymorphisms with the results found in a Mexican Mestizo population. METHODS: PAI-1 -675 4G/5G and PAI-2 Ser(413)/Cys were determined by the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique using Bsl I and Mwo I on four generations of the family studied. PAI-2 Ser(413)/Cys polymorphism was also determined in 50 healthy individuals of Mexican Mestizo origin. RESULTS: The family pedigree demonstrated that this family did not follow a Mendelian inheritance pattern. When the PAI-2 Ser(413)/Cys polymorphism was examined, we found that 60% (3/5) of the relatives homozygous to Ser(413)/Ser were affected with SLE and/or APS (p = 0.027). The proband case was 4G/5G genotype for the PAI-1 -675 4G/5G polymorphism. No differences between healthy controls of the Mexican Mestizo population and the family studied for the PAI-2 Ser(413)/Cys polymorphism or PAI-1 -675 4G/5G polymorphisms were found. CONCLUSIONS: Our data indicate that this family did not follow the Mendelian inheritance pattern. The Ser(413)/Ser genotype demonstrated in 60% of the affected members (3/5) of this family might increase the risk for autoimmune syndromes such as APS or SLE.

Methicillin resistance study in clinical isolates of coagulase-negative staphylococci and determination of their susceptibility to alternative antimicrobial agents.

AIMS: To achieve reliable detection of methicillin resistance in clinical isolates of coagulase-negative staphylococci. METHODS AND RESULTS: Strains (105) were evaluated by normatized antimicrobial susceptibility methods, and for the presence of the methicillin resistance-determining mecA gene, using the polymerase chain reaction. Correlation between phenotypic and genotypic methods was obtained in 87.6% of the samples. Six strains, classified as methicillin-susceptible by phenotypic assays, revealed the presence of the mecA gene, indicating that methicillin resistance expression was probably repressed. Another seven isolates failed to show mecA amplification after displaying methicillin resistance in phenotypic evaluations. The susceptibility of the methicillin-resistant isolates to other antimicrobial agents was variable. CONCLUSION: Genotypic determination of the mecA gene proved to be the most reliable method for detection of methicillin resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: Correct assessment of methicillin resistance, such as that attained through genotyping, is essential for defining therapeutic strategies, particularly when treating severely compromised patients.

Competition between C-terminal tyrosine and nicotinamide modulates pyridine nucleotide affinity and specificity in plant ferredoxin-NADP(+) reductase.

Chloroplast ferredoxin-NADP(+) reductase has a 32,000-fold preference for NADPH over NADH, consistent with its main physiological role of NADP(+) photoreduction for de novo carbohydrate biosynthesis. Although it is distant from the 2'-phosphoryl group of NADP(+), replacement of the C-terminal tyrosine (Tyr(308) in the pea enzyme) by Trp, Phe, Gly, and Ser produced enzyme forms in which the preference for NADPH over NADH was decreased about 2-, 10-, 300-, and 400-fold, respectively. Remarkably, in the case of the Y308S mutant, the k(cat) value for the NADH-dependent activity approached that of the NADPH-dependent activity of the wild-type enzyme. Furthermore, difference spectra of the NAD(+) complexes revealed that the nicotinamide ring of NAD(+) binds at nearly full occupancy in the active site of both the Y308G and Y308S mutants. These results correlate well with the k(cat) values obtained with these mutants in the NADH-ferricyanide reaction. The data presented support the hypothesis that specific recognition of the 2'-phosphate group of NADP(H) is required but not sufficient to ensure a high degree of discrimination against NAD(H) in ferredoxin-NADP(+) reductase. Thus, the C-terminal tyrosine enhances the specificity of the reductase for NADP(H) by destabilizing the interaction of a moiety common to both coenzymes, i.e. the nicotinamide.

The role of photosynthetic electron transport in the oxidative degradation of chloroplastic glutamine synthetase

The stability of chloroplastic glutamine synthetase (GS; EC 6.3.1.2) was investigated under photooxidative stress using wheat (Triticum aestivum L.) leaves, chloroplasts, and chloroplast lysates. Illuminated seedlings sprayed with the superoxide radical (O-(2)) propagator methyl viologen showed rapid GS decline dependent on MV concentration and exposure time. Degradation products of approximately 39 and 31 kD were detected when chloroplast lysates containing both stroma and thylakoids were illuminated in the presence of MV or H(2)O(2). In all cases, GS cleavage was prevented by the addition of the electron transport inhibitor 3-(3, 4-dichlorophenyl)-1,1-dimethylurea. Full protection against degradation could also be obtained by the incorporation of chelators or antioxidant enzymes. Maximal rates of degradation required the presence of transition metals and reducing compounds such as NADPH or dithiothreitol. Similar patterns of GS cleavage were obtained when seedlings were exposed to high doses of irradiation. The results indicate that chloroplastic GS is extremely prone to oxidative cleavage, and that reduced transition metals, presumably resulting from the destruction of iron-sulfur clusters by light-generated O-(2), play a crucial role in the degradation process. The physiological implications of GS lability to oxidative stress are discussed.

A productive NADP+ binding mode of ferredoxin-NADP + reductase revealed by protein engineering and crystallographic studies.

The flavoenzyme ferredoxin-NADP+ reductase (FNR) catalyzes the production of NADPH during photosynthesis. Whereas the structures of FNRs from spinach leaf and a cyanobacterium as well as many of their homologs have been solved, none of these studies has yielded a productive geometry of the flavin-nicotinamide interaction. Here, we show that this failure occurs because nicotinamide binding to wild type FNR involves the energetically unfavorable displacement of the C-terminal Tyr side chain. We used mutants of this residue (Tyr 308) of pea FNR to obtain the structures of productive NADP+ and NADPH complexes. These structures reveal a unique NADP+ binding mode in which the nicotinamide ring is not parallel to the flavin isoalloxazine ring, but lies against it at an angle of approximately 30 degrees, with the C4 atom 3 A from the flavin N5 atom.