Bioinspiration as a method of problem‐based STEM education: A case study with a class structured around the COVID‐19 crisis

Bioinspiration is a promising lens for biology instruction as it allows the instructor to focus on current issues, such as the COVID‐19 pandemic. From social distancing to oxygen stress, organisms have been tackling pandemic‐related problems for millions of years. What can we learn from such diverse adaptations in our own applications? This review uses a seminar course on the COVID‐19 crisis to illustrate bioinspiration as an approach to teaching biology content. At the start of the class, students mind‐mapped the entire problem; this range of subproblems was used to structure the biology content throughout the entire class. Students came to individual classes with a brainstormed list of biological systems that could serve as inspiration for a particular problem (e.g., absorptive leaves in response to the problem of toilet paper shortages). After exploration of relevant biology content, discussion returned to the focal problem. Students dug deeper into the literature in a group project on mask design and biological systems relevant to filtration and transparency. This class structure was an engaging way for students to learn principles from ecology, evolution, behavior, and physiology. Challenges with this course design revolved around the interdisciplinary and creative nature of the structure; for instance, the knowledge of the participants was often stretched by engineering details. While the present class was focused on the COVID‐19 crisis, a course structured through a bioinspired approach can be applied to other focal problems, or subject areas, giving instructors a powerful method to deliver interdisciplinary content in an integrated and inquiry‐driven way.     

Enzymatic pre‐treatment of microalgae cells for enhanced extraction of proteins

Crude proteins and pigments were extracted from different microalgae strains, both marine and freshwater. The effectiveness of enzymatic pre‐treatment prior to protein extraction was evaluated and compared to conventional techniques, including ultrasonication and high‐pressure water extraction. Enzymatic pre‐treatment was chosen as it could be carried out at mild shear conditions and does not subject the proteins to high temperatures, as with the ultrasonication approach. Using enzymatic pre‐treatment, the extracted proteins yields of all tested microalgae strains were approximately 0.7 mg per mg of dry cell weight. These values were comparable to those achieved using a commercial lytic kit. Ultrasonication was not very effective for proteins extraction from Chlorella sp., and the extracted proteins yields did not exceed 0.4 mg per mg of dry cell weight. For other strains, similar yields were achieved by both treatment methods. The time‐course effect of enzymatic incubation on the proteins extraction efficiency was more evident using laccase compared to lysozyme, which suggested that the former enzyme has a slower rate of cell disruption. The crude extracted proteins were fractionated using an ion exchange resin and were analyzed by the electrophoresis technique. They were further tested for their antioxidant activity, the highest of which was about 60% from Nannochloropsis sp. The total phenolic contents in the selected strains were also determined, with Chlorella sp. showing the highest content reaching 17 mg/g. Lysozyme was also found to enhance the extraction of pigments, with Chlorella sp. showing the highest pigments contents of 16.02, 4.59 and 5.22 mg/g of chlorophyll a, chlorophyll b and total carotenoids, respectively.     

Reaction of haem containing proteins and enzymes with hydroperoxides: The radical view

The reaction between hydroperoxides and the haem group of proteins and enzymes is important for the function of many enzymes but has also been implicated in a number of pathological conditions where oxygen binding proteins interact with hydrogen peroxide or other peroxides. The haem group in the oxidized Fe³⁺ (ferric) state reacts with hydroperoxides with a formation of the Fe⁴⁺=O (oxoferryl) haem state and a free radical primarily located on the π-system of the haem. The radical is then transferred to an amino acid residue of the protein and undergoes further transfer and transformation processes. The free radicals formed in this reaction are reviewed for a number of proteins and enzymes. Their previously published EPR spectra are analysed in a comparative way. The radicals directly detected in most systems are tyrosyl radicals and the peroxyl radicals formed on tryptophan and possibly cysteine. The locations of the radicals in the proteins have been reported as follows: Tyr133 in soybean leghaemoglobin; αTyr42, αTrp14, βTrp15, βCys93, (αTyr24−αHis20), all in the α- and β-subunits of human haemoglobin; Tyr103, Tyr151 and Trp14 in sperm whale myoglobin; Tyr103, Tyr146 and Trp14 in horse myoglobin; Trp14, Tyr103 and Cys110 in human Mb. The sequence of events leading to radical formation, transformation and transfer, both intra- and intermolecularly, is considered. The free radicals induced by peroxides in the enzymes are reviewed. Those include: lignin peroxidase, cytochrome c peroxidase, cytochrome c oxidase, turnip isoperoxidase 7, bovine catalase, two isoforms of prostaglandin H synthase, Mycobacterium tuberculosis and Synechocystis PCC6803 catalase-peroxidases.     

The relationship between subclinical atherosclerosis and electrocardiographic abnormalities as biomarkers of cardiovascular risk

Electrocardiographic findings indicating myocardial disease, such as left ventricular hypertrophy or ST-T wave abnormalities, or the presence of coronary artery calcium, indicating atherosclerotic coronary artery disease, are both biomarkers of future cardiovascular (CV) risk. Although the risk factors for myocardial and coronary artery disease are similar, their concomitant expression has implications for CV disease screening and prevention programmes. The relationship between the resting 12-lead ECG and subclinical atherosclerosis measured as coronary artery calcium (CAC) with electron beam tomography was examined in 937 healthy participants (aged 40-50 years) enrolled in a CV risk screening study. Electrocardiograms and CAC were interpreted in blinded fashion, using standard criteria. An abnormal ECG was coded in 268 (28.6%) participants, most commonly left ventricular hypertrophy (3.1%), delayed precordial R wave transition (5.7%), T-wave abnormalities (10.0%) and intraventricular conduction delay (10.4%). Although abnormal ECG findings were associated with CV risk variables, the prevalence of any CAC was similar in subjects with any ECG finding (43 of 268, 16.0%) compared with those with normal ECGs (125 of 669, 18.7%, p=NS). In a logistic model controlling for CV risk factors including systolic blood pressure, low-density lipoprotein cholesterol (LDL-C), body mass index (BMI), glycosylated haemoglobin, race, age and gender, significant associations with CAC were found for LDL-C, race and BMI. There was no significant relationship between CAC and ECG abnormalities (odds ratio 0.80, 95% confidence interval 0.54-1.20). In conclusion, electrocardiographic abnormalities and subclinical calcified atherosclerosis were not significantly associated with each other in this middle-aged screening population. This suggests these two biomarkers may be complementary towards broader detection of latent CV risk.     

Mn/Fe superoxide dismutase interaction fingerprints and prediction of oligomerization and metal cofactor from sequence

Fe- and Mn-containing superoxide dismutase (sod) enzymes are closely related and similar in both amino acid sequence and structure, but differ in their mode of oligomerization and in their specificity for the Fe or Mn cofactor. The goal of the present work is to identify and analyze the sequence and structure characteristics that ensure the cofactor specificities and the oligomerization modes. For that purpose, 374 sod sequences and 17 sod crystal structures were collected and aligned. These alignments were searched for residues and inter-residue interactions that are conserved within the whole sod family, or alternatively, that are specific to a given sod subfamily sharing common characteristics. This led us to define key residues and inter-residue interaction fingerprints in each subfamily. The comparison of these fingerprints allows, on a rational basis, the design of mutants likely to modulate the activity and/or specificity of the target sod, in good agreement with the available experimental results on known mutants. The key residues and interaction fingerprints are furthermore used to predict if a novel sequence corresponds to a sod enzyme, and if so, what type of sod it is. The predictions of this fingerprint method reach much higher scores and present much more discriminative power than the commonly used method that uses pairwise sequence comparisons.     

Constitutive heterochromatin: a surprising variety of expressed sequences

The organization of chromosomes into euchromatin and heterochromatin is amongst the most important and enigmatic aspects of genome evolution. Constitutive heterochromatin is a basic yet still poorly understood component of eukaryotic chromosomes, and its molecular characterization by means of standard genomic approaches is intrinsically difficult. Although recent evidence indicates that the presence of transcribed genes in constitutive heterochromatin is a conserved trait that accompanies the evolution of eukaryotic genomes, the term heterochromatin is still considered by many as synonymous of gene silencing. In this paper, we comprehensively review data that provide a clearer picture of transcribed sequences within constitutive heterochromatin, with a special emphasis on Drosophila and humans.     

The discovery of tertiary-amine LXR agonists with potent cholesterol efflux activity in macrophages

The liver X receptors (LXR) play a key role in cholesterol homeostasis and lipid metabolism. SAR studies around tertiary-amine lead molecule 2, an LXR full agonist, revealed that steric and conformational changes to the acetic acid and propanolamine groups produce dramatic effects on agonist efficacy and potency. The new analogs possess good functional activity, demonstrating the ability to upregulate LXR target genes, as well as promote cholesterol efflux in macrophages.