[Written tests analysis under the principles of authentic assessment. A comparative study of written tests of medical and other undergraduate programs]. / Análisis de pruebas escritas bajo los principios de la evaluación auténtica. Estudio comparativo entre carreras de la salud y otras carreras de dos universidades de la Región del Biobío.

BACKGROUND: Learning assessment has great impact in students' achievement. However, it is one of the least intervened and researched areas in higher education institutions, all over the world. AIM: To compare the written tests applied to students of three health science undergraduate programs (Speech Therapy, Medical Technology and Nursing), with the written tests of three programs of other areas (Business and Administration, Psychology and Bioengineering). MATERIAL AND METHODS: Comparisons were done using the Authentic Assessment Model's indicators. Also, the magnitude of the change in these variables was evaluated in these two groups of undergraduate programs, after the participation of the teachers in a training program based on this model. A quantitative and repeated measurements design was used. Nineteen teachers participated (nine from medical sciences and 10 from other areas), who drafted 88 written tests before the intervention (which involved 1,318 items) and 93 written tests (that grouped 1,051 items) after it. Items were analyzed using a Hierarchical Lineal Model (HLM), controlling the tests' and the teachers' effects. RESULTS: Both groups of undergraduate programs use multiple choice items with a higher frequency, although there were differences in the rest of the items. Also, HLM analysis showed that these programs differed in their changes after the intervention. Health science programs had less improvement in changing the kind of items used, but improved more in Authentic Assessment indicators. CONCLUSIONS: Written tests improved after an intervention aiming to improve the teachers' skills to prepare such tests.

Análisis de pruebas escritas bajo los principios de la evaluación auténtica: estudio comparativo entre carreras de la salud y otras carreras de dos universidades de la Región del Biobío / Written tests analysis under the principles of authentic assessment: a comparative study of written tests of medical and other undergraduate programs

Background: Learning assessment has great impact in students' achievement. However, it is one of the least intervened and researched areas in higher education institutions, all over the world. Aim: To compare the written tests applied to students of three health science undergraduate programs (Speech Therapy, Medical Technology and Nursing), with the written tests of three programs of other areas (Business and Administration, Psychology and Bioengineering). Material and Methods: Comparisons were done using the Authentic Assessment Model's indicators. Also, the magnitude of the change in these variables was evaluated in these two groups of undergraduate programs, after the participation of the teachers in a training program based on this model. A quantitative and repeated measurements design was used. Nineteen teachers participated (nine from medical sciences and 10 from other areas), who drafted 88 written tests before the intervention (which involved 1,318 items) and 93 written tests (that grouped 1,051 items) after it. Items were analyzed using a Hierarchical Lineal Model (HLM), controlling the tests' and the teachers' effects. Results: Both groups of undergraduate programs use multiple choice items with a higher frequency, although there were differences in the rest of the items. Also, HLM analysis showed that these programs differed in their changes after the intervention. Health science programs had less improvement in changing the kind of items used, but improved more in Authentic Assessment indicators. Conclusions: Written tests improved after an intervention aiming to improve the teachers' skills to prepare such tests.

Molecular and functional characterization of ferredoxin NADP(H) oxidoreductase from Gracilaria chilensis and its complex with ferredoxin.

BACKGROUD: Ferredoxin NADP(H) oxidoreductases (EC 1.18.1.2) (FNR) are flavoenzymes present in photosynthetic organisms; they are relevant for the production of reduced donors to redox reactions, i.e. in photosynthesis, the reduction of NADP+ to NADPH using the electrons provided by Ferredoxin (Fd), a small FeS soluble protein acceptor of electrons from PSI in chloroplasts. In rhodophyta no information about this system has been reported, this work is a contribution to the molecular and functional characterization of FNR from Gracilaria chilensis, also providing a structural analysis of the complex FNR/Fd. METHODS: The biochemical and kinetic characterization of FNR was performed from the enzyme purified from phycobilisomes enriched fractions. The sequence of the gene that codifies for the enzyme, was obtained using primers designed by comparison with sequences of Synechocystis and EST from Gracilaria. 5'RACE was used to confirm the absence of a CpcD domain in FNRPBS of Gracilaria chilensis. A three dimensional model for FNR and Fd, was built by comparative modeling and a model for the complex FNR: Fd by docking. RESULTS: The kinetic analysis shows KMNADPH of 12.5 M and a k cat of 86 s-1, data consistent with the parameters determined for the enzyme purified from a soluble extract. The sequence for FNR was obtained and translated to a protein of 33646 Da. A FAD and a NADP+ binding domain were clearly identified by sequence analysis as well as a chloroplast signal sequence. Phycobilisome binding domain, present in some cyanobacteria was absent. Transcriptome analysis of Gch revealed the presence of two Fd; FdL and FdS , sharing the motif CX5CX2CX29X. The analysis indicated that the most probable partner for FNR is FdS. CONCLUSION: The interaction model produced, was consistent with functional properties reported for FNR in plants leaves, and opens the possibilities for research in other rhodophyta of commercial interest.

Molecular and functional characterization of ferredoxin NADP(H) oxidoreductase from Gracilaria chilensis and its complex with ferredoxin

BACKGROUND: Ferredoxin NADP(H) oxidoreductases (EC 1.18.1.2) (FNR) are flavoenzymes present in photosynthetic organisms; they are relevant for the production of reduced donors to redox reactions, i.e. in photosynthesis, the reduction of NADP+ to NADPH using the electrons provided by Ferredoxin (Fd), a small FeS soluble protein acceptor of electrons from PSI in chloroplasts. In rhodophyta no information about this system has been reported, this work is a contribution to the molecular and functional characterization of FNR from Gracilaria chilensis, also providing a structural analysis of the complex FNR/Fd. METHODS: The biochemical and kinetic characterization of FNR was performed from the enzyme purified from phycobilisomes enriched fractions. The sequence of the gene that codifies for the enzyme, was obtained using primers designed by comparison with sequences of Synechocystis and EST from Gracilaria. 5'RACE was used to confirm the absence of a CpcD domain in FNRPBS of Gracilaria chilensis. A three dimensional model for FNR and Fd, was built by comparative modeling and a model for the complex FNR: Fd by docking. RESULTS: The kinetic analysis shows KMNADPH of 12.5 M and a kcat of 86 s-1, data consistent with the parameters determined for the enzyme purified from a soluble extract. The sequence for FNR was obtained and translated to a protein of 33646 Da. A FAD and a NADP+ binding domain were clearly identified by sequence analysis as well as a chloroplast signal sequence. Phycobilisome binding domain, present in some cyanobacteria was absent. Transcriptome analysis of Gch revealed the presence of two Fd; FdL and FdS, sharing the motif CX5CX2CX29X. The analysis indicated that the most probable partner for FNR is FdS. CONCLUSION: The interaction model produced, was consistent with functional properties reported for FNR in plants leaves, and opens the possibilities for research in other rhodophyta of commercial interest.

Evolution of the interaction between Runx2 and VDR, two transcription factors involved in osteoblastogenesis.

BACKGROUND: The mineralized skeleton is a major evolutionary novelty that has contributed to the impressive morphological diversifications of the vertebrates. Essential to bone biology is the solidified extracellular matrix secreted by highly specialized cells, the osteoblasts. We now have a rather complete view of the events underlying osteogenesis, from a cellular, molecular, genetic, and epigenetic perspective. Because this knowledge is still largely restricted to mammals, it is difficult, if not impossible, to deduce the evolutionary history of the regulatory network involved in osteoblasts specification and differentiation. In this study, we focused on the transcriptional regulators Runx2 and VDR (the Vitamin D Receptor) that, in mammals, directly interact together and stabilize complexes of co-activators and chromatin remodellers, thereby allowing the transcriptional activation of target genes involved in extracellular matrix mineralization. Using a combination of functional, biochemical, and histological approaches, we have asked if the interaction observed between Runx2 and VDR represents a recent mammalian innovation, or if it results from more ancient changes that have occurred deep in the vertebrate lineage. RESULTS: Using immunohistochemistry and in situ hybridization in developing embryos of chick, frog and teleost fishes, we have revealed that the co-expression of Runx2 and VDR in skeletal elements has been particularly strengthened in the lineage leading to amniotes. We show that the teleost Runx2 orthologue as well as the three mammalian Runx1, Runx2 and Runx3 paralogues are able to co-immunoprecipitate with the VDR protein present in nuclear extracts of rat osteoblasts stimulated with 1alpha,25-dihydroxyvitamin D3. In addition, the teleost Runx2 can activate the transcription of the mammalian osteocalcin promoter in transfection experiments, and this response can be further enhanced by 1alpha,25-dihydroxyvitamin D3. Finally, using pull-down experiments between recombinant proteins, we show that the VDR homologue from teleosts, but not from ascidians, is able to directly interact with the mammalian Runx2 homologue. CONCLUSIONS: We propose an evolutionary scenario for the assembly of the molecular machinery involving Runx2 and VDR in vertebrates. In the last common ancestor of actinopterygians and sacropterygians, the three Runx paralogues possessed the potential to physically and functionally interact with the VDR protein. Therefore, 1alpha,25-dihydroxyvitamin D3 might have been able to modulate the transcriptional activity of Runx1, Runx2 or Runx3 in the tissues expressing VDR. After the split from amphibians, in the lineage leading to amniotes, Runx2 and VDR became robustly co-expressed in developing skeletal elements, and their regulatory interaction was incorporated in the genetic program involved in the specification and differentiation of osteoblasts.

Crystallization and preliminary X-ray analysis of a domain in the Runx2 transcription factor that interacts with the 1alpha,25 dihydroxy vitamin D3 receptor.

The Runx2 transcription factor is a key regulator of osteoblast differentiation. In response to 1alpha,25 dihydroxy vitamin D3, Runx2 may interact with the 1alpha,25 dihydroxy vitamin D3 receptor (VDR) in the promoter of target genes, producing a synergic activation of their transcription. Previous studies have suggested that the motifs responsible for the VDR-Runx2 interaction are contained within the 230-361 domain of Runx2. In this work, we confirmed by GST-pull down that Runx2(I(209-361)) is sufficient to interact with the VDR. To obtain structural information, GST-Runx2(I(209-361)) protein was overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapor-diffusion method and polyethyleneglycol as a precipitant. The crystals were found to diffract to a maximum resolution of 2.7 A and a complete data set to a 3.3 A resolution was collected and analyzed. The crystals belong to the tetragonal system, with a space group P4 and unit-cell parameters of a = b = 90.8, and c = 57.2 A. The presence of a monomer of the recombinant GST-Runx2(I(209-361)) in the asymmetric unit gives a V(M) of 2.7 A(3) Da(-1) and a solvent content of 54.8%.

The structure at 2 A resolution of Phycocyanin from Gracilaria chilensis and the energy transfer network in a PC-PC complex.

Phycocyanin is a phycobiliprotein involved in light harvesting and conduction of light to the reaction centers in cyanobacteria and red algae. The structure of C-phycocyanin from Gracilaria chilensis was solved by X-ray crystallography at 2.0 A resolution in space group P2(1). An interaction model between two PC heterohexamers was built, followed by molecular dynamic refinement. The best model showed an inter-hexamer rotation of 23 degrees . The coordinates of a PC heterohexamer (alphabeta)(6) and of the PC-PC complex were used to perform energy transfer calculations between chromophores pairs using the fluorescence resonance energy transfer approach (FRET). Two main intra PC ((I)beta(3)(82)-->(I)alpha(1)(84)-->(I)alpha(5)(84)-->(I)beta(6)(82) and (I)beta(3)(153)-->(I)beta(5)(153)) and two main inter PC ((I)beta(6)(82)-->(II)beta(3)(82) and (I)beta(5)(153)-->(II)beta(3)(153)) pathways were proposed based on the values of the energy transfer constants calculated for all the chromophore pairs in the hexamer and in the complex.

Structural-functional analysis of the oligomeric protein R-phycoerythrin.

The structure of phycobiliproteins and their spatial organization in the phycobilisome provide the environment for high efficiency in light harvesting and conduction towards photosystem II. This article focuses on the analysis of R-phycoerythrin, a light harvesting hexameric phycobiliprotein that is part of the phycobilisomes. The interaction surfaces and the environment of the chromophores of R-phycoerythrin were studied in order to explain its structural stability and spectroscopic sensitivity, properties revealed by perturbation experiments. Three interaction surfaces are described (alpha beta), (alpha beta)3 and (alpha beta)6. The analysis shows the importance of alpha subunits in the interaction between trimers, the homodimeric nature of the monomer (alpha beta) and also the presence of anchor points in every interaction surface studied: alpha18Phe and beta18Tyr for (alpha beta), beta76Asn for (alpha beta)3 and alpha25Asn for (alpha beta)6. Side chains of arginine, lysine or glutamine residues are located in the proximity of the chromophores providing the correct stabilization of their carboxylates. Aspartic acids residues are associated through H-bonds to the N atom of the two central rings of the tetrapyrrolic chromophores. Changes in the spectroscopic properties are observed in perturbation experiments, confirming the spatial requirement for an efficient resonance energy transfer among chromophores and through the phycobilisome.

Structural-functional analysis of the oligomeric protein R-phycoerythrin

The structure of phycobiliproteins and their spatial organization in the phycobilisome provide the environment for high efficiency in light harvesting and conduction towards photosystem II. This article focuses on the analysis of R-phycoerythrin, a light harvesting hexameric phycobiliprotein that is part of the phycobilisomes. The interaction surfaces and the environment of the chromophores of R-phycoerythrin were studied in order to explain its structural stability and spectroscopic sensitivity, properties revealed by perturbation experiments. Three interaction surfaces are described (ab), (ab)3 and (ab)6. The analysis shows the importance of a subunits in the interaction between trimers, the homodimeric nature of the monomer (ab) and also the presence of anchor points in every interaction surface studied: a18Phe and b18Tyr for (ab), b76Asn for (ab)3 and a25Asn for (ab)6 . Side chains of arginine, lysine or glutamine residues are located in the proximity of the chromophores providing the correct stabilization of their carboxylates. Aspartic acids residues are associated through H-bonds to the N atom of the two central rings of the tetrapyrrolic chromophores. Changes in the spectroscopic properties are observed in perturbation experiments, confirming the spatial requirement for an efficient resonance energy transfer among chromophores and through the phycobilisome.