A very simple protocol for teaching Beer's Law and absorption spectrophotometry using a smart phone is described. Materials commonly found in high school chemistry laboratories or even around the house may be used. Data collection and analysis is quick and easy. Despite the simple nature of the experiment, excellent results can be achieved.

The separation of chamazulene from hydrophilic contaminants present in blue tansy oil provides a visually engaging example of two common techniques: extraction and thin-layer chromatography (TLC). This application uses liquid CO2 as a lipophilic solvent to pull a brilliant blue hydrocarbon molecule, chamazulene, out of or through a common hydrophilic material, cellulose. Yellow-green, hydrophilic components remain in a cotton ball or at the lower end of a paper strip. In dramatic fashion, the separation of colored components of blue tansy oil is accomplished with an environmentally sustainable solvent, CO2, and an innocuous support material, cellulose. We believe this is the first reported use of liquid CO2 in centrifuge tubes to conduct TLC.

Eukaryotic PsbO, the photosystem II (PSII) manganese-stabilizing protein, has two N-terminal sequences that are required for binding of two copies of the protein to PSII [Popelkova, H., et al. (2002) Biochemistry 41, 10038-10045; Popelkova, H., et al. (2003) Biochemistry 42, 6193-6200]. In the work reported here, a set of selected N-terminal truncation mutants of PsbO that affect subunit binding to PSII were used to determine the effects of PsbO stoichiometry on the Mn, Ca(2+), and Cl(-) cofactors and to characterize the roles of each of the PsbO subunits in PSII function. Results of the experiments with the PsbO-depleted PSII membranes reconstituted with the PsbO deletion mutants showed that the presence of PsbO does not affect Ca(2+) retention by PSII in steady-state assays of activity, nor is it required for Ca(2+) to protect the Mn cluster against reductive inhibition in darkness. In contrast to the results with Ca(2+), PsbO increases the affinity of Cl(-) for the active site of the O(2)-evolving complex (OEC) as expected. These results together with other data on activity retention suggest that PsbO can stabilize the Mn cluster by facilitating retention of Cl(-) in the OEC. The data presented here indicate that each of two copies of PsbO has a distinctive function in PSII. Binding of the first PsbO subunit fully stabilizes the Mn cluster and enhances Cl(-) retention, while binding of the second subunit optimizes Cl(-) retention, which in turn maximizes O(2) evolution activity. Nonspecific binding of some PsbO truncation mutants to PSII has no functional significance.

Protocols for examining the kinetics of CO 2 escape from solution during the popular Diet Coke and Mentos experiment have been explored. The methods developed allow teachers to demonstrate and students to explore various physicochemical processes involved when Mentos candies are placed in Diet Coke. For example, a pH meter can be used to observe a slight decrease in acidity as dissolved CO 2 escapes the soda. Furthermore, a balance or CO 2 sensor can be used to directly measure CO 2 escape. Arrhenius analysis of degassing rates determined using these latter methods yielded an activation energy of 25 kJ mol −1 for the conversion of CO 2 (aq) to CO 2 (g). The materials required for the experiments are easy to acquire and set up; therefore these investigations are amenable for use in high school and undergraduate chemistry classrooms and laboratories

The so-called Diet Coke and Mentos experiment is initiated by dropping Mentos candies into a bottle of Diet Coke or other carbonated beverage. This causes the beverage to rapidly degas, causing foam to stream out of the bottle. Simple application of the gas laws leads to the straightforward prediction that ejection of greater foam volume is expected at lower atmospheric pressure. This hypothesis is bolstered when principles of bubble physics are taken into account. This hypothesis was tested and confirmed by monitoring the foam produced during the Diet Coke and Mentos experiment at various altitudes above sea level. Upon further application of the aforementioned principles, a relationship between degassing kinetics, beverage CO2 concentration, and the size of pores on the candy surface that serve as nucleation sites can be derived. Using this relationship and experimental measurements of degassing kinetics, students estimated that the nucleation sites on Mentos candies are on the order of 2–7 μm in dimension. Students in Physical Chemistry, General Chemistry, and nonmajors’ courses have found these experiments to be of great interest.