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Scleroglucan, a comb-like branched (1 --> 3)-beta-D-glucan, dissolves in water as a stiff, triple-helical structure with the single glucose branches extending from the surface. The aim of this study is to investigate structural changes in the triple-helical structure associated with selective chemical modification of the side chains. Electron and atomic force microscopy, respectively, were used to investigate the macromolecular structures of aldehyde and carboxylated derivatives of scleroglucan-namely, scleraldehyde and sclerox-with different degrees of substitution. Scleraldehyde was observed to have structures resembling the triplex of the unmodified scleroglucan for all degrees of substitution up to 1.0. Additionally, an increasing tendency to aggregate for the higher degrees of substitution was observed. Fully carboxylated scleroglucan, sclerox(1.0), prepared from solutions at ionic strengths below 1.0M, revealed dispersed, flexible, coil-like structures. This indicates an electrostatic-driven strand separation of the scleroglucan triple-helical structure occurring concomitant with an increasing fraction of the side chains bearing carboxylate groups. Annealed sclerox(1.0) samples in aqueous 1.0 and 1.5M NaCl exhibited partly, or completely, reassociated triplex ensembles, with species ranging from apparently fully zipped linear and circular topologies, partly zipped structures with triplex strand separation occurring at the ends, to dispersed single-strands with random coil-like appearance. This study shows that periodate oxidation of the scleroglucan side chains is not a sufficient modification of the side chains to induce dissociation of the triple-helical structure, whereas further oxidation of the side chains to carboxylic groups dissociates the triple-helical structure when the degree of substitution is above 0.6., (Copyright 2001 John Wiley & Sons, Inc. Biopolymers 58: 535-547, 2001)

The immunomodulating properties of comb-like branched (1-->3)-beta-D-glucans scleroglucan, schizophyllan and lentinan depend on branching pattern, molecular weight and higher-order structure. The effect of weight average molecular weight Mw and higher order structure of scleroglucan, on stimulation of human monocytes cultured in vitro to secrete tumor necrosis factor-alpha (TNF-alpha) was investigated. The higher order structures of the scleroglucan samples were determined by electron microscopy. The data showed that the samples with a linear wormlike, triple helical structure with Mw less than 50 x 10(4) g/mol or larger than 110 x 10(4) g/mol stimulated the monocytes more efficiently than samples with Mw in the range (67-110) x 10(4) g/mol. The denaturation of the linear triple helices by NaOH (> 0.25 M), followed by neutralization yielded blends of linear and macrocyclic topologies with concomitant irreversible reduction of the cytokine inducing activity compared with the untreated scleroglucans. The dose-dependent ability to activate monocytes to cytokine production was not restored following annealing of the denatured-renatured samples, despite the fact that electron micrographs revealed similar structures of these annealed samples to the starting material. Pre-incubation of monocytes with antibodies against cluster of differentiation antigens CD14 or CD11b reduced the scleroglucan potency to stimulate TNF-alpha secretion mainly for mAb against CD14 in the presence of serum.

The expression of the melanoma-associated antigen p250 on thermotolerant cells and the effect of a second heat dose on the antigen expression have been measured by flow cytometry. The human melanoma cell line FME was heated at 43.5 degrees C for 120 min after a priming heat dose at 43.5 degrees C for 20, 40 or 60 min. Cells preheated at 43.5 degrees C for 40 and 60 min followed the same kinetics of development and decay of thermotolerance, with maximum thermotolerance 16 h after the priming heating, and the thermotolerance had decayed by 48 h. Cells preheated at 43.5 degrees C for 20 min showed maximum thermotolerance after 7 h and decay by 24 h. Heat reduced the expression of the melanoma-associated antigen in a dose-dependent manner. Thermotolerant cells were given a second heat dose (43.5 degrees C for 120 min) and the antigen expression measured immediately after heating. Fractionated hyperthermia using the lower predose (43.5 degrees C for 20 min) might have an additive effect on the reduction of antigen expression, while the highest predose (43.5 degrees C for 60 min) protected against reduction in antigen expression. The development and decay of resistance against heat-induced reduction in expression of melanoma-associated antigen followed a similar time course as thermotolerance in terms of cell survival. Maximum resistance was observed 12 h after the priming heat treatment, and the resistance had decayed by 48 h.

A series of monogalactosyl diacylglycerols was isolated from lipophilic extracts of Fischerella ambigua. These glycolipids were identified on the basis of chemical and spectroscopic analyses.

A total of 80 lipophilic and hydrophilic extracts obtained from 20 samples of cultured freshwater and terrestrial cyanobacteria were investigated for their biological activities. Of all the extracts, 26% exhibited a significant lethal effect against brine shrimp. Out of 54 extracts tested for antimicrobial activity, 78% showed antibacterial and 45% antifungal activities. Of 30 extracts tested for cytotoxicity against KB cells, none was found to be active. Bioassay-guided fractionation of the lipophilic extracts of Fischerella ambigua led to the isolation of three compounds; ambigols A (1) and B (2), and tjipanazole D (3). Compounds 1 and 2 exhibited antibacterial, antifungal, cytotoxic, molluscicidal, and anti-inflammatory, and antiviral activities. Tjipanazole D (3) showed moderate antibacterial properties.