ALBERT

Description: A new class of pH-sensitive indicator dyes for optical carbon dioxide sensors based on di-OH-aza-BODIPYs is presented. These colorimetric indicators show absorption maxima in the near infrared range (λmax 670–700 nm for the neutral form, λmax 725–760 nm for the mono-anionic form, λmax 785–830 nm for the di-anionic form), high molar absorption coefficients of up to 77 000 M−1 cm−1 and unmatched photostability. Depending on the electron-withdrawing or electron-donating effect of the substituents the pKa values are tunable (8.7–10.7). Therefore, optical carbon dioxide sensors based on the presented dyes cover diverse dynamic ranges (0.007–2 kPa; 0.18–20 kPa and 0.2–100 kPa), which enables different applications varying from marine science and environmental monitoring to food packaging. The sensors are outstandingly photostable in the absence and presence of carbon dioxide and can be read out via absorption or via the luminescence-based ratiometric scheme using the absorption-modulated inner-filter effect. Monitoring of the carbon dioxide production/consumption of a Hebe plant is demonstrated.

Description: Red blood cell (RBC)-based micromotors containing both therapeutic and diagnostic modalities are described as a means for potential theranostic applications. In this natural RBC-based multicargo-loaded micromotor system, quantum dots (QDs), anti-cancer drug doxorubicin (DOX), and magnetic nanoparticles (MNPs), were co-encapsulated into RBC micromotors. The fluorescent emission of both QDs and DOX provides direct visualization of their loading inside the RBC motors at two distinct wavelengths. The presence of MNPs within the RBCs allows for efficient magnetic guidance under ultrasound propulsion along with providing the potential for magnetic resonance imaging. The simultaneous encapsulation of the imaging nanoparticles and therapeutic payloads within the same RBC micromotor has a minimal effect upon its propulsion behavior. The ability of the RBC micromotors to transport imaging and therapeutic agents at high speed and spatial precision through a complex microchannel network is also demonstrated. Such ability to load and transport diagnostic imaging agents and therapeutic drugs within a single cell-based motor, in addition to a lower toxicity observed once the drug is encapsulated within the multicargo RBC motor, opens the door to the development of theranostic micromotors that may simultaneously treat and monitor diseases.

Description: This is a new golden age for drug discovery based on natural products derived from both marine and terrestrial sources. Herein, a straightforward but important question is “what are the major structural differences between marine natural products (MNPs) and terrestrial natural products (TNPs)?” To answer this question, we analyzed the important physicochemical properties, structural features, and drug-likeness of the two types of natural products and discussed their differences from the perspective of evolution. In general, MNPs have lower solubility and are often larger than TNPs. On average, particularly from the perspective of unique fragments and scaffolds, MNPs usually possess more long chains and large rings, especially 8- to 10-membered rings. MNPs also have more nitrogen atoms and halogens, notably bromines, and fewer oxygen atoms, suggesting that MNPs may be synthesized by more diverse biosynthetic pathways than TNPs. Analysis of the frequently occurring Murcko frameworks in MNPs and TNPS also reveals a striking difference between MNPs and TNPs. The scaffolds of the former tend to be longer and often contain ester bonds connected to 10-membered rings, while the scaffolds of the latter tend to be shorter and often bear more stable ring systems and bond types. Besides, the prediction from the naïve Bayesian drug-likeness classification model suggests that most compounds in MNPs and TNPs are drug-like, although MNPs are slightly more drug-like than TNPs. We believe that MNPs and TNPs with novel drug-like scaffolds have great potential to be drug leads or drug candidates in drug discovery campaigns.

Description: Methane bubble formation and transport is an important component of biogeochemical carbon cycling in aquatic sediments. To improve understanding of how sediment mechanical properties influence bubble growth and transport in freshwater sediments, a 20-day laboratory incubation experiment using homogenized natural clay and sand was performed. Methane bubble development at high resolution was characterized by μCT. Initially, capillary invasion by microbubbles (〈0.1 mm) dominated bubble formation, with continued gas production (4 days for clay; 8 days for sand), large bubbles formed by deforming the surrounding sediment, leading to enhanced of macropore connectivity in both sediments. Growth of large bubbles (〉1 mm) was possible in low shear yield strength sediments (〈100 Pa), where excess gas pressure was sufficient to displace the sediment. Lower within the sand, higher shear yield strength (〉360 Pa) resulted in a predominance of microbubbles where the required capillary entry pressure was low. Enhanced bubble migration, triggered by a controlled reduction in hydrostatic head, was observed throughout the clay column, while in sand mobile bubbles were restricted to the upper 6 cm. The observed macropore network was the dominant path for bubble movement and release in both sediments.

Description: Alkylresorcinols are amphiphilic metabolites, well-known for their diverse biological activities, produced by both prokaryotes and eukaryotes. A few classes of alkylresorcinol scaffolds have been reported from the photoautotrophic cyanobacteria, ranging from the relatively simple hierridins to the more intricate cylindrocyclophanes. Recently, it has emerged that cyanobacteria employ two different biosynthetic pathways to produce unique alkylresorcinol scaffolds. However, these convergent pathways intersect by sharing biosynthetic elements which lead to common structural motifs. To obtain a broader view of the biochemical diversity of these compounds in cyanobacteria, we comprehensively cover the isolation, structure, biological activity and biosynthesis of their mono- and dialkylresorcinols. Moreover, we provide an overview of the diversity and distribution of alkylresorcinol-generating biosynthetic gene clusters in this phylum and highlight opportunities for discovery of novel alkylresorcinol scaffolds. Because some of these molecules have inspired notable syntheses, different approaches used to build these molecules in the laboratory are showcased.

Description: The first inter-calibration study of the stable silicon isotope composition of dissolved silicic acid in seawater, δ30Si(OH)4, is presented as a contribution to the international GEOTRACES program. Eleven laboratories from seven countries analyzed two seawater samples from the north Pacific subtropical gyre (Station ALOHA) collected at 300 m and at 1000 m water depth. Sampling depths were chosen to obtain samples with a relatively low (9 μmol L-1, 300 m) and a relatively high (113 μmol L-1, 1000 m) silicic acid concentration as sample preparation differs for low- and high- concentration samples. Data for the 1000m water sample were not normally distributed so the median is used to represent the central tendency for the two samples. Median δ30Si(OH)4 values of +1.66 ‰ for the low-concentration sample and +1.25 ‰ for the high-concentration sample were obtained. Agreement among laboratories is overall considered very good; however, small but statistically significant differences among the mean isotope values obtained by different laboratories were detected likely reflecting interlaboratory differences in chemical preparation including pre-concentration and purification methods together with different volumes of seawater volume analyzed, and the use of different mass spectrometers including the Neptune MC-ICP-MS (Thermo Fisher™, Germany), the Nu Plasma MC-ICP-MS (Nu Instruments™, Wrexham, UK), and the Finnigan™ (now Thermo Fisher™, Germany) MAT 252 IRMS. Future studies analyzing δ30Si(OH)4 in seawater should also analyze and report values for these same two reference waters in order to facilitate comparison of data generated among and within laboratories over time.