Lead (Pb2+) sorptive removal using chitosan-modified biochar: batch and fixed-bed studies.

Chitosan-Modified fast pyrolysis BioChar (CMBC) was used to remove Pb2+ from water. CMBC was made by mixing pine wood biochar with a 2% aqueous acetic acid chitosan (85% deacylated chitin) solution followed by treatment with NaOH. The characterizations of both CMBC and Non-Modified BioChar (NMBC) were done using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy (SEM), surface area measurements (S BET), elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and ζ-potential measurements. Elemental analysis indicated that chitosan accounts for about 25% weight of the CMBC. The Langmuir maximum adsorption capacity of CMBC at pH 5 was 134 mg g-1 versus 48.2 mg g-1 for NMBC at 318 K. CMBC column adsorption studies resulted in a capacity of 5.8 mg g-1 (Pb2+ conc. 150 mg L-1; pH 5; column dia 1.0 cm; column length 20 cm; bed height 5.0 cm; flow rate 2.5 mL min-1). CMBC removed more Pb2+ than NMBC suggesting that modification with chitosan generates amine groups on the biochar surface which enhance Pb2+ adsorption. The modes of Pb2+ adsorption on CMBC were studied by comparing DRIFTS and X-ray photoelectron spectroscopy spectra before and after Pb2+ adsorption.

The cytoskeleton and motility in apicomplexan invasion.

We consider the cytoskeletal structure, function, and motility of the invasive zoites of the Apicomplexa. This monophyletic group possess a prominent microtubular cytoskeleton, with a very distinct polarity. It is associated with a non-actin based filamentous system, and with a cisternal double membrane assembly beneath the plasma membrane. The origin of the microtubular cytoskeleton is a set of apical rings. Its role in motility is still unclear, but the present knowledge of apicomplexan tubulins' molecular biology and chemistry is outlined. Actin and accessory proteins are present, and it is apparent that actin polymerisation is tightly controlled in zoites. It does not contribute to the cytoskeleton ordinarily, but is crucial in the acto-myosin linear motor which drives gliding, capping, and invasion, the best understood aspects of zoite motility. Several myosins distinct from the primary linear motor myosin are also found, but not yet well understood functionally. Many of the myosins fall into a class of the superfamily so far seen only in this phylum. The possible relationships of the actin, myosin, cytoskeletal linkage proteins, and external force-transducing adherent proteins are discussed.