Effects of structure and modification on sustained release properties of starches

Starches of different sources and compositions were investigated to determine the effect of structure and chemical modification on the sustained release properties of the resultant modified starches. Starches were cross-linked with epichlorohydrin and substituted with carboxymethyl or aminoethyl groups at different levels. Substitution efficiency was overall higher for waxy corn and potato starches than for Hylon VII, and was higher for starches at low cross-linking levels than those at high cross-linking ones. Waxy corn starch displayed better sustained release properties when cross-linked to a lower level, whereas Hylon VII showed better performances when cross-linked to a higher level. Matrices substituted with carboxymethyl and aminoethyl groups at the high level showed better sustained release properties than those substituted at the low level. The proportion and structure of amylose and amylopectin in starches from different botanical sources strongly influenced the level of modification required to produce a satisfactory sustained release matrix.     

The control of transmembrane helix transverse position in membranes by hydrophilic residues

The ability of hydrophilic residues to shift the transverse position of transmembrane (TM) helices within bilayers was studied in model membrane vesicles. Transverse shifts were detected by fluorescence measurements of the membrane depth of a Trp residue at the center of a hydrophobic sequence. They were also estimated from the effective length of the TM-spanning sequence, derived from the stability of the TM configuration under conditions of negative hydrophobic mismatch. Hydrophilic residues (at the fifth position in a 21-residue hydrophobic sequence composed of alternating Leu and Ala residues and flanked on both ends by two Lys) induced transverse shifts that moved the hydrophilic residue closer to the membrane surface. At pH 7, the dependence of the extent of shift upon the identity of the hydrophilic residue increased in the order: L < GYT < RH < S < P < K < EQ < N < D. By varying pH, shifts with ionizable residues fully charged or uncharged were measured, and the extent of shift increased in the order: L < GYH^oT < E^oR < S < P < K⁺< QD^oH⁺ < NE^– < D^–. The dependence of transverse shifts upon hydrophilic residue identity was consistent with the hypothesis that shift magnitude is largely controlled by the combination of side chain hydrophilicity, ionization state, and ability to position polar groups near the bilayer surface (snorkeling). Additional experiments showed that shift was also modulated by the position of the hydrophilic residue in the sequence and the hydrophobicity of the sequence moved out of the bilayer core upon shifting. Combined, these studies show that the insertion boundaries of TM helices are very sensitive to sequence, and can be altered even by weakly hydrophilic residues. Thus, many TM helices may have the capacity to exist in more than one transverse position. Knowledge of the magnitudes of transverse shifts induced by different hydrophilic residues should be useful for design of mutagenesis studies measuring the effect of transverse TM helix position upon function.     

New starches: Physicochemical properties of sweetsop (Annona squamosa) and soursop (Anonna muricata) starches

Starch from the fruits of sweetsop (Anonna squamosa) and soursop (Anonna muricata) were isolated and purified and the fat, ash, phosphorus and protein contents measured. The amount of amylose present was determined spectrophotometrically and found to be very similar (19%) for both starches. Scanning electron microscopy showed very small indented and spherical granules from both with an average granule size of 4.84 μm and 4.72 μm, respectively. The physicochemical properties, namely the swelling power, solubility, pasting characteristics, paste clarity and freeze–thaw stability were studied to assess the functionality of the starch pastes as hydrocolloids. The sweetsop starch showed higher swelling power and solubility compared to soursop starch and had a lower gelatinization temperature indicating a weaker granular structure. Sweetsop starch exhibited a lower pasting temperature, higher viscosity peak, higher viscosity breakdown and lower setback, higher paste clarity and freeze–thaw stability compared to soursop starch. The low gelatinization temperature and high freeze thaw stability of sweetsop starch are comparable to that of waxy corn. The properties of sweetsop indicate that it has potential for application as a thickener in frozen foods.     

Biodiversity of living benthic foraminifera: How many species are there?

In ecological studies involving the analysis of  2.4 million living (stained) individual tests, to date  2140 species of benthic foraminifera have been recorded. Of these 602 species are agglutinated, 341 porcelaneous and 1197 hyaline. The numbers of species in the major environments are: marginal marine 701 (in  1.5 million individuals), shelf 989 (in  0.6 million individuals) and deep sea 831 (in  0.3 million individuals). 381 species occur in more than one major environment. Overall  33% have abundance of > 10% while  67% are of minor abundance (< 10%). The majority of species are rare, most are endemic and very few are cosmopolitan (5% or less). To estimate the potential total number of living species the following factors need to be quantified: the proportion of species already named (here considered unlikely to be less than 50% of the potential total), the number of species currently known to be dead but for which living representatives may yet to be found (assumed to be 5% = 107 species), and the proportion of species that are synonyms (10–25% = 214 to 535 species). Assuming that 50% of species have already been named (2140 + 107 = 2247), the potential total ranges from  3959 to  4280 species for 10% synonymy to  3210 to  3531 species for 25% synonymy.     

Fine structure characterization of amylopectins from grain amaranth starch

The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with α-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then β-amylase to remove all external chains, whereby the internal structure was obtained. The ,β-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC–PAD). The results showed that the domain fraction contained 2.2 clusters, and single clusters were composed of 13 chains. The ,β-limit dextrins of the clusters were further hydrolyzed with α-amylase to characterize their building block composition. The average DP of the branched blocks was 11 and they contained on average 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of 6 branched blocks, and the internal chain length between the blocks was 6.8.     

Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography

An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 ( 7.0–5.9 Ma). The Gurabo Formation spans Zones N18 and N19 ( 5.9–4.5 Ma). The Mao Formation is placed in Zone N19 ( 4.5–3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific–Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation ( 6.1 Ma) and in the middle Mao Formation ( 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity ( 4.8 Ma) and periods of upwelling ( 6.1and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity, and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes.     

Reaction pattern of a novel thermostable α-amylase

A novel thermostable α-amylase, D45 was studied for its reaction pattern on starch hydrolysis. Fine structures of the dextrins and oligosaccharides produced by D45 were determined and compared with those produced by other thermostable α-amylases, Termamyl^®LC (LC) and Termamyl^®SC (SC). Waxy maize starch dispersion was hydrolyzed with LC, SC and D45 at different concentrations to obtain hydrolysates with the same dextrose equivalent value (DE). At DE 13, molecular weight distribution of dextrins produced by D45 displayed a mono-distribution with a peak centered at degree of polymerization (DP) of 7, whereas LC and SC hydrolysates displayed a bimodal-distribution of the molecular weight profiles with one peak centered at DP 5 and the other at DP 34. Thin-layer chromatograms (TLC) showed that DP 2, 3, 5, 6 and 7 were the primary oligosaccharides produced in LC hydrolysate, DP 4–7 in SC hydrolysate, and DP 6–9 in D45 hydrolysate. Comparison of the decrease in the blue color of amylose-iodine complex at 620 nm (blue value) with the increase in reducing value for the hydrolysis of amylose by LC, SC and D45 showed that for an equivalent decrease in blue value, LC and SC produced a higher percentage of reducing sugar than did D45. The results suggest that D45 has a greater degree of random attack (multichain) reaction, whereas LC and SC have more multiple-attack reactions.     

Extraction and characterization of hemicelluloses from flax shives by different methods

Hemicelluloses were extracted from flax shives using pressurized low-polarity water (PLPW), pressurized aqueous ethanol (PAE), microwave-assisted water (MW-Water) or aqueous ethanol (MW-EtOH), and precipitated with ethanol. Hemicelluloses still remaining in solution were further separated using ultrafiltration. All samples were characterized with chemical analysis, ion-moderated partition chromatography (IMP), size exclusion chromatography (SEC), and Fourier transform infrared (FT-IR) spectroscopy. PLPW, PAE, MW-Water and MW-EtOH extracted 90, 80, 18, and 40% of the total hemicelluloses, respectively. The molecular weight of the ethanol-precipitated hemicelluloses ranged from approximately 11,000 to 40,000 Da and the ethanol-soluble low-molecular weight hemicelluloses were about 1700 Da. High-molecular weight hemicellulose isolated from PAE extracts contained 23% lignin, while that from the PLPW extracts contained 5% lignin. Low-molecular weight hemicelluloses separated by ultrafiltration from PLPW and PAE extracts contained similar amounts of lignin (20%). However, the yield of low-molecular weight hemicelluloses from PLPW was higher (15%) compared to that from PAE (6%). The FT-IR results revealed the specific band maximum at 1220 cm⁻¹ and the bands between 1175 and 1000 cm⁻¹ which are typical of xylans.     

Early Neogene biochemostratigraphy of Pohang Basin: a paleoceanographic response to the early opening of the Sea of Japan (East Sea)

The location of the Pohang Basin near the Korea Strait in the southwest of the Sea of Japan (East Sea) makes this area appropriate for providing a record of paleoenvironmental/biotic changes associated with the early Neogene (16.5 Ma) opening of this gateway to the Pacific Ocean. Stable isotopic and planktonic foraminiferal records are presented that assist with the understanding of paleoenvironmental changes in the Sea of Japan resulting from the opening of the Korea Strait. The oldest sediments of early Neogene age of the Pohang Basin overlie Cretaceous basement and are Early Miocene (>16.5 Ma) shallow, estuarine facies containing a benthic foraminiferal assemblage dominated by Ammonia beccarii (L.). The oldest early Neogene planktonic foraminiferal assemblages in the basin are 16.5 Ma in age (latest Early Miocene foraminiferal zone N8). The migration of these planktonic assemblages to the Sea of Japan at that time appears to have resulted from the initial opening of the Korea Strait. The overlying early Neogene marine sequence of the Pohang Basin extends from 16.5 Ma (Zone N8) through 14 Ma (Zone N10). Change in the oxygen isotopic record of the Pohang Basin sequence suggests strong local paleoenvironmental control related to the early opening of the Korea Strait. Early Middle Miocene isotopic temperatures of planktonic foraminifera are relatively cool at 15 Ma at a time when global temperatures were high in the middle/low latitude regions. It was not until 14.8 Ma that isotopic temperatures of planktonic foraminifera increased markedly. This distinct warming is inferred to reflect the major intrusion of the Kuroshio Current into the Sea of Japan probably as a result of further critical opening and deepening of the Korea Strait. At this time planktonic foraminifera increased in abundance reflecting expanding oceanic influence. A cooling that followed at 14.5 Ma, when the strait was well open is unlikely to reflect local tectonic control on the paleoceanography, but global cooling during the early Middle Miocene associated with the expansion of the East Antarctic ice sheet.     

Initiation of motility by steelhead (Oncorhynchus mykiss) sperm: membrane ion exchangers and pH sensitivity

Initiation of motility in salmonid sperm is sensitive to the pH of the extracellular medium, however, the basis of this sensitivity is not clear. Sperm incubated in an immobilization buffer (SI) at low pH ( 7.1–7.2) become motile when diluted with activating medium (AM) at high ( 8.5) but not low pH. Based on this observation, various agents were tested to determine whether the onset of steelhead sperm motility upon activation with high pH AM, following incubation with low pH SI, could be blocked by inhibiting membrane exchangers postulated to be important in intracellular pH (pHi) regulation. Amiloride (inhibitor of proton:sodium exchange), SITS and DIDS (inhibitors of anion exchange) and bafilomycin A 1 (inhibitor of H⁺-ATPase activity) were not effective in this experimental design. However, regardless of SI pH, DIDS was effective in blocking motility as was replacing chloride with thiocyanate or including the chloride channel blocker, niflumic acid, in SI suggesting that chloride efflux plays a key role in motility initiation. Nonetheless, the results of this study suggest that the rapid onset of sperm motility with activation at high pH following incubation at low pH is probably not based on rapid adjustment of pHi via membrane exchangers/transporters but rather due to an effect of pH on motility-associated processes at the extracellular surface of the sperm.     

Propionic acid production from glycerol by metabolically engineered Propionibacterium acidipropionici

Large amounts of crude glycerol produced in the biodiesel industry can be used as a low-cost renewable feedstock to produce chemicals and fuels. Compared to sugars (sucrose, glucose, xylose, etc.), glycerol has a lower reducing level, which is of benefit to the production of reduced chemicals. In this work, glycerol as the sole carbon source in propionic acid fermentation by metabolically engineered Propionibacterium acidipropionici (ACK-Tet) was studied. It was found that the adapted ACK-Tet mutant could use glycerol for its growth and produced propionic acid at a high yield of 0.54–0.71 g/g, which was much higher than that from glucose (0.35 g/g). In addition, the production of acetic acid in glycerol fermentation was much less than that from glucose. Thus, glycerol fermentation produced a high purity propionic acid with a high propionic acid to acetic acid ratio of 22.4 (vs. 5 for glucose fermentation), facilitating the recovery and purification of propionic acid from the fermentation broth. The highest propionic acid concentration obtained from glycerol fermentation was 106 g/L, which was 2.5 times of the highest concentration (42 g/L) previously reported in the literature.     

Optimization of glutaryl-7-aminocephalosporanic acid acylase expression in E. coli

A recombinant glutaryl-7-aminocephalosporanic acid acylase (GLA) from Pseudomonas N176 has been over-expressed in BL21(DE3)pLysS Escherichia coli cells. By alternating screenings of medium components and simplified factorial experimental designs, an improved microbial process was set up at shake-flask level (and then scaled up to 2L-fermentors) giving a 80- and 120-fold increase in specific and volumetric enzyme productivity, respectively. Under the best expression conditions, 1380 U/g cell and 16,100 U/L of GLA were produced versus the 18 U/g cell and the 140 U/L obtained in the initial standard conditions. Osmotic stress caused by the addition of NaCl, low cell growth rate linked to high biomass yield in the properly-designed rich medium, optimization of the time and the amount of inducer’s addition and decrease of temperature during recombinant protein production, represent the factors concurring to achieve the reported expression level. Notably, this expression level is significantly higher than any previously described production of GLAs. High volumetric production, cost reduction and the simple one-step chromatographic purification of the His-tagged recombinant enzyme, makes this GLA an economic tool to be used in the 7-ACA industrial production.     

The Pandinus imperator haemolymph lipoprotein, an unusual phosphatidylserine carrying lipoprotein

The haemolymph lipoprotein of the scorpion, Pandinus imperator was isolated and characterised. Contrary to the lipoproteins of insects and the discoidal HDL-lipoproteins of a crayfish and polychaete, the Pandinus lipoprotein consists of three instead of two apoproteins (apoPiLp I = 230 kDa, apoPiLp II = 130 kDa and apoPiLp III = 120 kDa). The apolipoproteins are arranged in varying stoichiometries as judged by cross-linking experiments. In lipoprotein samples from individual animals, the two smaller subunits occurred in a 1:1 stoichiometry, while the relative amount of the 230 kDa peptide varied. The lipoprotein is a slightly heart-shaped HDL with a diameter of 15 nm. It is present in two densities of 1100 and 1190 kg/m³, of which the latter is by far more abundant. The native molecular mass was estimated to be 500 kDa. The lipid content was determined as 33.5% and consists of 70% neutral lipids and 30% phospholipids. Strikingly, 42.5% of the phospholipids is phosphatidylserine while phosphatidylcholine and phosphatidylethanolamine account for 55.1% and 2.3%, respectively. Carbohydrate analysis suggests the presence of only high-mannose-type N-glycans. N-glycan profiling shows glycans corresponding to a size of 8.0–11.5 hexose units.     

Synthesis of novel ketoconazole derivatives as inhibitors of the human Pregnane X Receptor (PXR; NR1I2; also termed SXR, PAR)

PXR, pregnane X receptor, in its activated state, is a validated target for controlling certain drug–drug interactions in humans. In this context, there is a paucity of inhibitors directed toward activated PXR. Using prior observations with ketoconazole as a PXR inhibitor, the target compound 3 was synthesized from (s)-glycidol with overall 56% yield. (+)-Glycidol was reacted with 4-bromophenol and potassium carbonate in DMF to yield the ring opened compound 6. This was then heated to reflux in benzene along with 2′, 4′-difluoroacetophenone and catalytic amount of para-toluene sulfonic acid to yield 8. The resultant acetal 8 was then functionalized using Palladium chemistry to yield the target compound 3. The activity of the compound was compared with ketoconazole and UCL2158H. However, in contrast with ketoconazole (IC₅₀  0.020 μM; 100% inhibition), 3 has negligible effects on inhibition of microsomal CYP450 (maximum 20% inhibition) at concentrations >40 μM. In vitro, micromolar concentration of ketoconazole is toxic to passaged human cell lines, while 3 does not exhibit cytotoxicity up to concentrations 100 μM (viability >85%). This is the first demonstration of a chemical analog of a PXR inhibitor that retains activity against activated PXR. Furthermore, in contrast with ketoconazole, 3 is less toxic in human cell lines and has negligible CYP450 activity.     

Inoculative releases of Trichogramma ostriniae for suppression of Ostrinia nubilalis (European corn borer) in sweet corn: field biology and population dynamics

The effectiveness of inoculative releases of Trichogramma ostriniae Pang and Chen for suppression of Ostrinia nubilalis (Hübner) in sweet corn was assessed. Early-season, low-density (75,000 females ha⁻¹) releases were made, and establishment, levels of parasitism and sex ratios of emerging T. ostriniae quantified. T. ostriniae established effectively for each season that they were released, but appeared to be unable to overwinter. Parasitism levels tracked egg mass numbers closely, and T. ostriniae persisted in fields even where insecticides were applied. Parasitism by indigenous Trichogramma species was 3%. Field populations of T. ostriniae were distinctly female biased (78%), with males produced in the majority of broods. Numbers of males did not increase linearly with number of O. nubilalis eggs parasitized, but appeared to remain constant above an egg mass size of about 20 eggs. A Type-I functional response to increasing egg and egg mass density was found under field conditions, where the proportion of egg masses parasitized remained constant with increasing egg mass density. A relatively consistent percentage of eggs per egg mass was parasitized, with a linear increase in number of eggs parasitized with increasing number of eggs per egg mass. These results show that T. ostriniae established viable reproductive populations in sweet corn following inoculative release, with the potential to contribute to reduced dependence on insecticides for the control of O. nubilalis in an integrated pest management program.     

Characterization of acid-induced molten globule like state of ficin

Effect of pH on the conformational behaviour of ficin (EC 3.4.22.3), a cysteine protease from the latex of Ficus carica was monitored by circular dichroism, fluorescence spectroscopy, ANS binding and hydrodynamic studies. The results obtained from near- and far-UV CD, intrinsic fluorescence and ANS binding studies demonstrate that ficin exhibits the characteristic properties of molten globule at acidic conditions between pH 1.4 and 2.0. Ficin at pH 1.4 retained about 74% secondary structure with a substantial loss of tertiary structure. The acid-induced state was found to have a compact shape as measured by Stokes radius on size exclusion chromatography.     

Pronase digestion of brush border membrane-bound Cry1Aa shows that almost the whole activated Cry1Aa molecule penetrates into the membrane

Bacillus thuringiensis insecticidal proteins, Cry toxins, following ingestion by insect larvae, induce insecticidal effect by penetrating the brush border membranes (BBM) of midgut epithelial cells. Purified, activated B. thuringiensis Cry1Aa bound to Bombyx mori BBMV or unbound Cry1Aa were vigorously digested with Pronase. Both digests were compared by Western blotting. Free Cry1Aa was digested to α-helix and/or to amino acids at 1 mg Pronase/mL within 2.4 h at 37 °C. Whereas, BBMV-bound Cry1Aa was very resistant to Pronase digestion and even at 2 mg for 24 h, 7.5 kDa and 30 kDa peptide were detected by α-2,3 antiserum, and α-4,5 and α-6,7 antisera, respectively. Another 30 kDa peptide was also detected by β-6-11 and domain III antisera. These fragments are believed either to be embedded in or to strongly interact with the BBMV. The 7.5 and former 30 kDa peptides are thought to be derived from α-2,3 helix and stretch of α-4 to α-7 helices. Furthermore the latter 30 kDa was thought to include the stretch of β-6 to domain III. Moreover, the embedded Cry1Aa molecule appears to be segregated in some areas of β-1-5 sheets, resulting in the above two 30 kDa peptides. From these digestion patterns, we proposed new membrane insertion model for single Cry1Aa molecule. On the other hand, in digestion of BBMV-bound Cry1Aa, 15 kDa peptide which was recognized only by α-4,5 antiserum was observed. This fragment must be dimeric α-4,5 helices and we discussed the origin of this peptide.     

CCK-8S activates c-Fos in a dose-dependent manner in nesfatin-1 immunoreactive neurons in the paraventricular nucleus of the hypothalamus and in the nucleus of the solitary tract of the brainstem

Recently, a new neuropeptide, named nesfatin-1, was discovered. It has been reported that nesfatin-1 inhibits food intake after injection into the third ventricle as well as intraperitoneal (ip) injection. Cholecystokinin (CCK) is well established to play a role in the regulation of food intake. The aim of the study was to examine whether CCK-8S injected ip modulates neuronal activity in nesfatin-1 immunoreactive (ir) neurons localized in the PVN and in the nucleus of the solitary tract (NTS). Additionally, tyrosine hydroxylase-immunoreactivity (TH-ir) in the PVN was determined to assess the distribution of TH-ir fibers in relation to nesfatin-1-ir. Non-fasted male Sprague-Dawley rats received 6 or 10 µg CCK-8S/kg or vehicle solution (0.15 M NaCl; n = 4 all groups) ip. The number of c-Fos-ir neurons was determined in the PVN, arcuate nucleus (ARC), and NTS. Double staining procedure for nesfatin-1 and c-Fos revealed that CCK-8S increased significantly and in a dose-dependent manner the number of c-Fos positive nesfatin-1-ir neurons in the PVN ( 4-fold and 7-fold) and NTS ( 9-fold and 26-fold). Triple staining in the PVN showed a dose-dependent neuronal activation of nesfatin-1 neurons that were colocalized with CRF and oxytocin. Double labeling against nesfatin-1 and TH revealed that nefatin-1-ir neurons were encircled in a network of TH-ir fibers in the PVN. No effect on the number of c-Fos-ir neurons was observed in the ARC. These results suggest that the effects of CCK on the HPA axis and on food intake may, at least in part, be mediated by nesfatin-1-ir neurons in the PVN.     

Western equatorial Pacific planktic foraminiferal fluxes and assemblages during a La Niña year (1999)

A correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies. We studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time-series sediment trap deployments in the western equatorial Pacific under La Niña conditions from January to November 1999. Eleven species contributed about 90% of the total flux in all traps. Two sites (MT1, MT3) in the Western Pacific Warm Pool region (WPWP) were characterized by common occurrences of the species Globigerinoides ruber, Globigerinoides sacculifer, Globigerinoides tenellus, and Neogloboquadrina dutertrei. Site MT5 farther to the east in the equatorial upwelling region had common occurrences of Globigerina bulloides, Globigerinita glutinata, and Pulleniatina obliquiloculata. Very high abundances of G. bulloides and G. glutinata at MT5 indicate that equatorial upwelling (EU) occurred during the 1999 La Niña. The two western sites have similar assemblage compositions, but MT1 ( 135°E) has the highest fluxes (up to  3800 tests m^− 2 day^− 1), whereas MT3 ( 145° E) has fluxes below  2200 tests m^− 2 day^− 1. Relatively high fluxes (up to  3000 tests m^− 2 day^− 1) occur at site MT5 ( 176° E), where upwelling occurred.The differences in faunal composition in the WPWP and EU might be attributable to differences in the way in which nutrients are supplied to the phytoplankton: large amounts of suspended material are supplied to the WPWP by advection of waters passing through the coastal region of an archipelago, whereas upwelling of nutrient-rich waters enhances primary production in the EU. At the westernmost site in the WPWP, a peak in the G. bulloides flux coincided with southward flow of the New Guinea Coastal Current (NGCC) in late February, but the highest G. ruber flux coincided with northward flow of this current in late May. Thus, the differences in species dominance at this location may be caused by monsoon-driven variability in the flow direction of the NGGC.     

Polyelectrolyte complex formation using alginate and chitosan

Polyelectrolyte complexes (PECs) of alginate and chitosan were formed by addition of 0.1% alginate solution (pH 6.5) to 0.1% chitosan solution (pH 4.0), and by adding the chitosan solution to the alginate solution under high shearing conditions. Variations in the properties of the polymers and the preparation procedure were studied, and the resultant PEC size, zeta potential (Zp), and pH were determined using dynamic light scattering (DLS), electrophoresis and by measuring turbidity and pH. Tapping mode atomic force microscopy (AFM) was used to examine some of the complexes. The particle size was decreased as the speed and diameter of the dispersing element of the homogenizer was increased. The net charge ratio between chitosan and alginate, and the molecular weights (M_W) of both the alginate and chitosan samples were the most significant parameters that influenced the particle size, Zp, and pH. The mixing order also influenced the size of the PECs, however, the Zp and pH were not affected by the mixing order. The stability of the complexes was investigated by incubation at an elevated temperature (37 °C), storage for one month at 4 °C, alteration of the pH of the PEC mixture, and addition of salt to physiological ionic strength (0.15 M NaCl). The properties of the PEC could be affected according to the molecular properties of the polyelectrolytes selected and the preparation procedures used. The resultant PEC sizes and properties of the complex were rationalised using a core-shell model for the structure of the complexes.