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Hydroxypropylation and cross-linking were carried out on three rice starches with 6.93%, 19.02% and 48.41% AAC respectively. AAC affected the efficiency of modification, with AAC increased, the molar substitution of hydroxypropylated starch decreased while degree of substitution of cross-linked starch increased. Modifications decreased starch relative crystallinity while the impacts were dependent on rice varieties. Starch granules of high AAC rice were liable to be disrupted by modification. High AAC rice starch had better processability, modifications have more pronounced influences on starch properties of high AAC. Different modifications showed different influences on starch properties, cross-linking decreased AAC content, pasting clarity and swelling power of all three starches, while hydroxypropylation increased pasting clarity and swelling power of high AAC starch. High-degree modifications decreased starch digestibility, higher-CLD crosslinked starch showed constant digestion rate and might be a suitable modification for produce starchy food for equilibrium glucose level.

An ultrasensitive photoelectrochemical (PEC) aptasensor was designed for detection of chloramphenicol (CAP) based on graphene quantum dots-sensitized TiO2 nanotube arrays (GQDs/TiO2 NTs). The GQDs/TiO2 NTs nanohybrids were prepared by a coupling technique of linker molecule binding and electrophoretic deposition. It exhibited significantly enhanced visible-light photoelectrochemical activity, which was firstly employed as the photoactive material for fabrication of PEC aptasensor. As the recognition unit, the aptamers of CAP were immobilized on GQDs/TiO2 NTs photoelectrode via π–π stacking interaction between GQDs and the nucleobases of the aptamer. In this signal-on proposal, the aptasensor was used for the label-free analysis of CAP by monitoring the increase in photocurrent that resulted from the formation of aptamer-CAP bioaffinity complexes with ascorbic acid as an efficient electron donor for scavenging photogenerated holes. Under the optimized conditions, the aptasensor showed a wide linear range from 0.5 nM to 100 nM for CAP detection with a low detection limit of 57.9 pM (S/N = 3). With good selectivity and sensitivity, the PEC aptasensor was applied to the determination of CAP in spiked honey samples with satisfactory results, suggesting that the GQDs/TiO2 NTs photoelectrode has a promising application in constructing PEC sensor platform.

Dietary fiber has several benefits for humans, and the development of healthier rice with an improved dietary fiber composition has attracted increasing amounts of attention. Based on the method of AOAC 2002.02, we developed a simplified method to screen polished rice containing high total dietary fiber (TDF). Mutant cw with a high TDF content could be distinguished easily from R7954 (indica) and Nipponbare (japonica) by the digestion-resistant phenotype, which is characterized as an almost intact grain after hydrolysis by pepsin, pancreatic α-amylase and amyloglucosidase. The individuals identified from the F2 population showed digestion resistance all had TDF content higher than 5%, while those without a digestion-resistant phenotype had TDF content lower than 5%. The phenotype of digestion resistance could be a valuable index for identifying rice with higher TDF content, and the identification of this phenotype provides a simplified, economical and high throughput method for high TDF rice breeding.

Zinc oxide nanoparticles (Nano-ZnO) are widely used in sunscreens, clothes, medicine and electronic devices. However, the potential risks of human exposure and the potential for adverse health impacts are not well understood. Previous studies have demonstrated that exposure to Nano-ZnO caused liver damage and hepatocyte apoptosis through oxidative stress, but the molecular mechanisms that are involved in Nano-ZnO-induced hepatotoxicity are still unclear. Endoplasmic reticulum (ER) is sensitive to oxidative stress, and also plays a crucial role in oxidative stress-induced damage. Previous studies showed that ER stress was involved in many chemical-induced liver injuries. We hypothesized that exposure to Nano-ZnO caused oxidative stress and ER stress that were involved in Nano-ZnO-induced liver injury. To test our hypothesis, mice were gavaged with 200 mg/kg or 400 mg/kg of Nano-ZnO once a day for a period of 90 days, and blood and liver tissues were obtained for study. Our results showed that exposure to Nano-ZnO caused liver injury that was reflected by focal hepatocellular necrosis, congestive dilation of central veins, and significantly increased alanine transaminase (ALT) and aspartate transaminase (AST) levels. Exposure to Nano-ZnO also caused depletion of glutathione (GSH) in the liver tissues. In addition, our electron microscope results showed that ER swelling and ribosomal degranulation were observed in the liver tissues from mice treated with Nano-ZnO. The mRNA expression levels of ER stress-associated genes (grp78, grp94, pdi-3, xbp-1) were also up-regulated in Nano-ZnO-treated mice. Nano-ZnO caused increased phosphorylation of RNA-dependent protein kinase-like ER kinase (PERK) and eukaryotic initiation factor 2α (eIF2α). Finally, we found that exposure to Nano-ZnO caused increased ER stress-associated apoptotic protein levels, such as caspase-3, caspase-9, caspase-12, phosphorylation of JNK, and CHOP/GADD153, and up-regulation of pro-apoptotic genes (chop and bax). These results suggest that oxidative stress and ER stress-induced apoptosis are involved in Nano-ZnO-induced hepatotoxicity in mice.

To acquire a better understanding of whether RS influences the dynamics of in vivo starch digestion and seed vigour, the high-RS rice mutant RS4 (RS ca. 10%) and the wild type R7954 were used to investigate total amylase activity, seedling vigour, starch content and starch granule structure during germination. RS4 exhibited similar seed vigour to R7954. Amylose and amylopectin in R7954 showed synchronous degradation throughout the whole process, while amylopectin was hydrolysed significantly faster than amylose in RS4 during the earlier germination stages. The starch residues of RS4 after germination (GD) lost endotherm peaks and showed a special X-ray diffraction pattern with only two peaks at around 16.90° and 21.62°, probably due to remnants of amylopectin and its tight crosslinking with the cell wall. The remaining starch after 10 GD, primarily amylopectin may make a critical contribution to total resistant starch content. These results indicated that RS had no negative impact on seed vigour in rice lines, although RS cannot be hydrolysed by α-amylase from human and animal in vitro . By appropriately increasing the special amylopectin fraction, a new breeding programme of high RS crops and improvement in the eating quality of high RS rice varieties might be achieved.

Three rice mutants with different contents of resistant starch (RS) were selected to investigate the effects of grain filling process on the formation of resistant starch. During grain development, the content of RS was increased with grain maturation and showed negative correlations with the grain weight and the starch molecular weight (Mn, Mw) and a positive correlation with the distribution of molecular mass (polydispersity, Pd). The morphologies of starch granules in high-RS rice were almost uniform in single starch granules and exhibited different proliferation modes from common rice. The lower activities of ADP-glucose pyrophosphorylase and starch branching enzyme and the higher activity of starch synthase and starch de-branching enzyme observed in high-RS rice might be responsible for the formation of small irregular starch granules with large spaces between them. In addition, the lower molecular weight and the broad distribution of molecular weights lead to differences in the physiochemical properties of starch.

The mechanism responsible for the effects of endogenous lipids on starch functionality is not fully understood. In this study, a high-lipid rice mutant (GZ1), a low apparent amylose content (AAC) mutant (GZ93) and parent rice (R7954) were employed to study the effect of the removal of starch lipids (SL) and non-starch lipids (NSL) on the physicochemical properties of starch and resistant starch (RS) and the rice gel texture. GZ1 had a lipid content of 2.52%, of which 61.1% was NSL. Removal of NSL only had a slight impact on the AAC, RS content, gelatinization temperature, swelling power and paste viscosity, but further removal of SL significantly increased the AAC and RS contents. For R7954 and GZ93, removal of SL decreased Tp, ΔH, PKV, CPV, and BDV but significantly increased the swelling power (SP). In GZI, the removal of SL resulted in significant increases in ΔH, PKV, HPV, CPV, SBV and the hardness of the gel texture. These results suggested that SLs had a much greater influence on the starch physicochemical properties and gel texture than NSLs. The results may be helpful in designing breeding programs for new rice varieties with better functionality.

RS2 and RS3 are two of the main resistant starch types in food, and the primary types found in raw and cooked rice respectively. To elucidate the physiochemical determinants for RS2 and RS3 content in rice, this study investigated the fine amylopectin structure, starch granules morphologies and starch pasting properties of nine different rice accessions. The results revealed that not all the accessions showed a decrease in resistant starch after cooking and cooling. Granular size, paste properties, fb1 and fb3 showed a significant negative correlation with RS3, whereas fa showed a significant positive correlation with RS3. RS2 had no significant correlation with granular size, but did have a significant positive correlation with HPV, CPV and fb2. Different rice types could be distinguished by the fine amylopectin structure of DP6-12 and DP13-24 chains. Taken together fa, fb2 and HPV and CPV values may have the potential to be used as indices for distinguishing or characterising rice with different RS2 and RS3 contents.

Through integrated molecular and biochemical investigations and by using a common mutant line in molecular mapping, we have shown that the SSIIa gene, previously reported to be responsible for the starch granule gelatinization temperature (GT) differences between indica and japonica rice varieties, might also control the GT variations among certain indica varieties. This effect is mediated through differences in the amounts of SSIIa protein bound to starch granules leading to differences in the structure of amylopectin molecules synthesized. For the first time it was shown, that the amylopectin type accounted only for the GT differences between varieties with different SSIIa alleles, but not between varieties carrying a common SSIIa allele. In the latter case, another gene, alk2(t) , with a genetic distance of 3.93 cM from the Wx gene, was identified as being responsible for the GT variations. Based on the thermal properties and amylopectin chain length profile characteristics, it is postulated that the SSIIa gene has at least three different alleles, one in japonica rice and two in indica rice varieties, whereas alk2(t) has at least two alleles for either low or high GT. Thus, the rich diversity of the GT character in rice very probably results from various combinations of these alleles.