Effect of hydrolysis time, pH and surfactant type on stability of hydrochloric acid hydrolyzed nanocellulose.

Nanocelluloses are the subject of much interest on the account of their mechanical properties, high surface area, porosity, etc. Typically, sulfuric acid is used to produce cellulose nanocrystals with high aspect ratio and dispersibility in water suspensions. However, hydrolysis in sulfuric acid leads to cellulose esterification, which has some drawbacks such as lower thermal stability of nanocellulose. Hydrochloric acid does not cause functionalization of the nanocellulose surface, yet yields in poor colloidal stability in aqueous solutions due to the lack of ionic interactions between CNC/CNF and water molecules. Therefore, it should be possible to tune the colloidal stability of nanocellulose aqueous suspensions by modifying the properties of the solution (such as pH and/or the presence of surfactants). In this work, we attempted to obtain stable aqueous CNF suspensions via hydrochloric acid hydrolysis. Hydrolysis was performed at three time intervals, at 60 °C temperature and 6 mol/dm3 of hydrochloric acid. To find the optimum stabilizing conditions, the effect of different pH values and various surfactants on CNF stability was explored. The best stabilizing effect was observed at pH range 5-9 and in nonionic surfactant. The obtained products were characterized by using spectroscopic (FTIR), microscopic (AFM), thermogravimetric and X-ray diffraction techniques.

DIAPH2 alterations increase cellular motility and may contribute to the metastatic potential of laryngeal squamous cell carcinoma.

Low 5-year survival rate in laryngeal squamous cell carcinoma (LSCC) is to large extent attributable to high rate of recurrences and metastases. Despite the importance of the latter process, its complex genetic background remains not fully understood. Recently, we identified two metastasis-related candidate genes, DIAPH2 and DIAPH3 to be frequently targeted by hemizygous/homozygous deletions, respectively, in LSCC cell lines. They physiologically regulate such processes as cell movement and adhesion, hence we found it as a rationale, to study if tumor LSCC specimens harbor mutations of these genes and whether the mutations are associated with metastasizing tumors. As a proof of concept, we sequenced both genes in five LSCC cell lines derived from lymph node metastases assuming there the highest probability of finding alterations. Indeed, we identified one hemizygous deletion (c.3116_3240del125) in DIAPH2 targeting the FH2 domain. Moreover, we analyzed 95 LSCC tumors (53 N0 and 42 N+) using the Illumina platform and identified three heterozygous single nucleotide variants in DIAPH2 targeting conserved domains exclusively in N+ tumors. By combining these results with cBioPortal data we showed significant enrichment of DIAPH2 mutations (P = 0.036) in N+ tumors. To demonstrate the consequences of DIAPH2 inactivation, CRISPR/Cas9 editing was used to obtain a heterozygous DIAPH2+/- mutant HEK-293T cell line. Importantly, the edited line shows a shift from 'proliferation' to 'migration' phenotype typically observed in metastasizing cells. In conclusion, we report that DIAPH2 alterations are present primarily in metastasizing specimens of LSCC and suggest that they may contribute to the metastatic potential of the tumor.

Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea.

It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south-north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes. The opposite trend was observed for autotrophs. The chlorophyll a (Chl a): carbon (C) ratio increased while the levels of photoprotective pigments decreased from south to north, indicating adaptation to the darker humic-rich water in the north. Picocyanobacteria dominated in phosphorus-rich areas while nanoplankton increased in ADOM-rich areas. During the winter-spring the phytoplankton biomass and concentrations of photoprotective pigments were low, and no trends with respect to autotrophs and mixotrophs were observed. Microplankton was the dominant size group in the entire study area. We conclude that changes in the size structure of the phytoplankton community, the Chl a:C ratio and the concentrations of photoprotective pigments are indicative of changes in ADOM, a factor of particular importance in a changing climate.

Allochthonous Carbon--a Major Driver of Bacterioplankton Production in the Subarctic Northern Baltic Sea.

Heterotrophic bacteria are, in many aquatic systems, reliant on autochthonous organic carbon as their energy source. One exception is low-productive humic lakes, where allochthonous dissolved organic matter (ADOM) is the major driver. We hypothesized that bacterial production (BP) is similarly regulated in subarctic estuaries that receive large amounts of riverine material. BP and potential explanatory factors were measured during May-August 2011 in the subarctic Råne Estuary, northern Sweden. The highest BP was observed in spring, concomitant with the spring river-flush and the lowest rates occurred during summer when primary production (PP) peaked. PLS correlations showed that ∼60% of the BP variation was explained by different ADOM components, measured as humic substances, dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM). On average, BP was threefold higher than PP. The bioavailability of allochthonous dissolved organic carbon (ADOC) exhibited large spatial and temporal variation; however, the average value was low, ∼2%. Bioassay analysis showed that BP in the near-shore area was potentially carbon limited early in the season, while BP at seaward stations was more commonly limited by nitrogen-phosphorus. Nevertheless, the bioassay indicated that ADOC could contribute significantly to the in situ BP, ∼60%. We conclude that ADOM is a regulator of BP in the studied estuary. Thus, projected climate-induced increases in river discharge suggest that BP will increase in subarctic coastal areas during the coming century.