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Es presenten les reflexions sobre didàctica de les ciències generades a partir de les revisions del material didàctic AICLE (ciències naturals en anglès) per a 1r d’ESO, realizades a la UAB durant les tutories amb la Dra. Cristina Escobar, de Didàctica de la Llengua, i la Dra. Neus Sanmartí, de Didàctica de les Ciències. Els materials han estat experimentats a l’Institut Montserrat amb un grup de 30 alumnes gràcies al Pla Experimental de Llengües Estrangeres concedit pel Departament d’Educació.

A lyotropic chiral liquid crystal consisting of organic solutions of poly-gamma-benzyl-L-glutamate (PBLG) provides an appropriate medium for the observation of proton decoupled deuterium NMR spectra of enatiomers. Liquid crystals consisting of PBLG organic solutions show different deuterium NMR spectra for each enatiomer due to the interaction of enatiomers with chiral centers of the PBLG helix and their different orientation in the medium. The technique used is convenient in use and general in application.

Proton-decoupled deuterium NMR study uses poly(gamma-benzyl L-glutamate) as an orientation matrix to observe enantiomers of the compounds, which are chiral by virtue of H/D isotopic substitution. The chirality does not arise from the asymmetric molecular ordering, and few enantiomers exhibit different molecular ordering due to geometrical differences between protonated and deuterated molecules. NMR spectrum of CHD2-OH has separate signals for each enantiotropic deuterons.

Deuterium NMR in cholesteric lyotropic liquid crystal solvent can be used to elucidate the enantiomers of deuterated methylene amino esters, synthesized from their respective amino acids, and their enantiomeric purity can be assessed. This method finds general and differentiating applicability by virtue of its simplicity and the sensitivity to the ee measurement.

In cloud water, microorganisms are exposed to very strong stresses especially related to the presence of reactive oxygen species including H 2 O 2 and radicals, which are the driving force of cloud chemistry. In order to understand how the bacterium Pseudomonas graminis isolated from cloud water respond to this oxidative stress, it was incubated in microcosms containing a synthetic solution of cloud water in the presence or in the absence of H 2 O 2 . P. graminis metabolome was examined by LC-MS and NMR after 50 min and after 24 hours of incubation. After 50 min, the cells were metabolizing H 2 O 2 while this compound was still present in the medium, and it was completely biodegraded after 24 hours. Cells exposed to H 2 O 2 had a distinct metabolome as compared to unexposed cells, revealing modulations of certain metabolic pathways in response to oxidative stress. These data indicated that the regulations observed mainly involved carbohydrate, glutathione, energy, lipid, peptides and amino-acids metabolisms. When cells had detoxified H 2 O 2 from the medium, their metabolome was not distinguishable anymore from unexposed cells, highlighting the capacity of resilience of this bacterium. This work illustrates the interactions existing between the cloud microbial metabolome and cloud chemistry.

Introduction: Active microorganisms have been recently discovered in clouds, thus demonstrating the capacity of microorganisms to exist in harsh environments, including exposure to UV and oxidants, osmotic and cold shocks, etc. It is important to understand how microorganisms respond to and survive such stresses at the metabolic level., Objectives: The objective of this work is to assess metabolome modulation in a strain of Pseudomonas syringae isolated from cloud water and facing temperature downshift from 17 to 5 °C by identifying key molecules and pathways of the response/adaptation to cold shock., Methods: Bacterial extracts from suspensions of cells grown at 17 °C and further incubated in microcosms at 5 and 17 °C to mimic cloud conditions were analysed by combining LC-MS and NMR; the results were evaluated in comparison to similar suspensions kept at constant temperature. The differences in the metabolome profiles were deciphered using multivariate statistics (PLS-DA)., Results: Key cold shock biomarkers were observed, including cryoprotectants (trehalose, glucose, glycerol, carnitine, glutamate), antioxidants (glutathione and carnitine) and their precursors, alkaloids (bellendine and slaframine) and metabolites involved in energy metabolism (ATP, carbohydrates). Furthermore, new short peptides (nine dipeptides and a tetrapeptide) were found that have no known function., Conclusions: This study shows that in response to cold temperatures, Pseudomonas syringae PDD-32b-74 demonstrates numerous metabolism modifications to counteract the impacts of low temperatures.

The beta-D-glucans from the cell wall of Saccharomyces cerevisiae have shown in vitro affinity for zearalenone. For this reason, their utilization as dietary adsorbent, to reduce the bioavailability of zearalenone, is of practical interest. Our study used powerful devices to elucidate the spatial conformation and molecular sites of interaction between ZEN and beta-D-glucans. In this respect, 1H NMR spectroscopy implicated the hydroxyl groups of the phenol moiety of zearalenone in the complexation by laminarin, a pure beta-(1,3)-D-glucan. X-ray diffraction determined that laminarin displays the conformation of a single-helix with six beta-D-glucopyranose residues per turn. At this stage, molecular modeling was useful to locate the interaction sites and to propose highly probable complexes of zearalenone with laminarin fragment. Interestingly, the beta-(1,3)-D-glucan chain favors a very stable intra-helical association with zearalenone, nicely stabilized by beta-(1,6)-D-glucans side chains. Both hydrogen bonds and van der Waals interactions were precisely identified in the complex and could thus be proposed as driving interactions to monitor the association between the two molecules.

Objective: To determine the impact of the particle repositioning maneuver on posterior canal benign paroxysmal positional vertigo-related quality of life using the Medical Outcomes Study 36-Item Short Form Health Survey and the Dizziness Handicap Inventory Short Form., Study Design: Prospective, consecutive new cases of posterior canal benign paroxysmal positional vertigo., Setting: Ambulatory, primary referral hospital., Patients: Forty individuals with posterior canal benign paroxysmal positional vertigo were investigated. The diagnosis was made on the basis of the history of recurrent sudden crisis of vertigo and positional-induced nystagmus during the Dix-Hallpike test., Interventions: All patients were treated by a single particle repositioning maneuver, and relapses were investigated at Days 7 and 30 posttreatment., Main Outcome Measures: Percentage of patients with negative Dix-Hallpike test after treatment, scores obtained on the 36-Item Short Form Health Survey and Dizziness Handicap Inventory Short Form before and 30 days after treatment., Results: DHT was found negative in 76% (28 of 37) individuals at 30 days. The eight scales of the 36-Item Short Form Health Survey had a good internal consistency reliability (Cronbach's alpha > 0.7) in patients with posterior canal benign paroxysmal positional vertigo. The average standardized score for each 36-Item Short Form Health Survey scale was compared with the reference population normative data, showing differences with norms for all scales, except for Vitality. After particle repositioning maneuver, patients scored closer to norms, and Social Function and Mental Health scores were significantly higher than the scores obtained before the particle repositioning maneuver (p < 0.05). Dizziness Handicap Inventory Short Form total score significantly decreased from 18.05 +/- 9.91 (mean +/- standard deviation) at the first day to 9.54 +/- 9.94 at 30 days (p < 0.001). All 36-Item Short Form Health Survey scale scores were correlated significantly with Dizziness Handicap Inventory Short Form total scores at 30 days after treatment., Conclusions: Posterior canal benign paroxysmal positional vertigo has a significant impact on health-related quality of life, and patients experienced a decrease in quality of life as compared with norms. The particle repositioning maneuver improves health-related quality of life in posterior canal benign paroxysmal positional vertigo.

The X-ray structure of [Zn(4-bromocalcimycin)2 x H2O] complex shows two highly different conformations of the ligand in the dimeric association, unusual in this ionophore family.

Objective: To identify pre or intraoperative risk factors that could indicate a higher risk for post-tonsillectomy hemorrhage (PTH) in children undergoing electrocautery dissection. SET-UP: Primary referral hospital., Design: A retrospective study of 163 post-tonsillectomy children comparing 7 cases of PTH with 156 cases with no PTH., Sample: This study includes children under the age of 18 that underwent tonsillectomy by dissection between 1997 and 2000., Outcome Parameters: Age, sex, height, weight, body mass index, hemoglobin level, hematocrit, platelet count activated partial thromboplastin time (APTT), fibrinogen, ASA index (physical state classification of the American Society of Anesthesiology) and type of hemostasis., Results: Prevalence of PTH was 4.29% in the cohort sample. The risk of PTH in children following tonsillectomy by electrodissection is significantly increased in patients over 15 years of age (OR = 8.46, p = 0.04) and when ligatures are used for hemostasis (OR = 8.62, p = 0.02). Activated partial thromboplastin time > or = 32 seconds is marginally significant (OR = 7.82, p = 0.05)., Conclusions: Our findings show that tonsillectomy by electrodissection has an increased risk of bleeding in older children and when ligatures are used for hemostasis.