Modification with Organometallic Compounds Improves Crossing of the Blood–Brain Barrier of [Leu5]‐Enkephalin Derivatives in an In Vitro Model System

Enkephalin peptides are thought to be suitable vectors for the passage of the blood–brain barrier (BBB). Modifications that do not alter the amino acid sequence are often used to improve the permeation through living membrane systems. As a new type of modification we introduce organometallic compounds, in particular ferrocene carboxylic acid. Derivatives of [Leu⁵]enkephalin were synthesised and labelled with organometallic compounds by using solid‐phase synthesis techniques. All new metal–peptide bioconjugates were comprehensively characterised by HPLC, NMR spectroscopy and mass spectrometry and found to be at least 95 % pure. For the first time, permeation coefficients in a BBB model for organometal–peptide derivatives were determined in this work. The uptake and localisation of fluorescein‐labelled enkephalins was monitored by fluorescence microscopy on three cancer cell lines. Octanol/H₂O partition coefficients of the compounds were measured by HPLC. The introduction of the organometallic moiety enhances the uptake into cells and the permeation coefficient of [Leu⁵]‐enkephalin. This could be due to an increase in lipophilicity caused by the organometallic label. The metal–peptide conjugates were found to be nontoxic up to mM concentrations. The low cytotoxicity encourages further experiments that could take advantage of the selectivity of enkephalin derivatives for opioid receptors.     

Quantitative detection of lactic acid bacteria in dried sourdoughs using real-time PCR

A real-time PCR system with 16S rRNA gene-targeted group-specific primers was developed to quantitatively detect lactic acid bacteria (LAB) of the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella in different types of commercially available dried sourdoughs. Despite a high degree of degradation in the DNA isolated from the doughs, the 341-bp 16S rRNA gene fragment of the sourdough LAB biota could specifically be amplified. For dried sourdoughs, the resulting calculated LAB cell counts were determined to be up to 3.7 × 10⁷ cells/g fresh dough, whereas in non-fermented dough acidifiers, used as a control, the calculated LAB cell counts did not exceed 3.6 × 10⁴ cells/g fresh dough. Moreover, the effect of low pH and/or high lactic acid concentrations prevailing in the doughs on the detectability of LAB cells in spray- and roller-dried sourdoughs by PCR was investigated. Drying of non-acidified sourdoughs still permitted to detect the LAB cells by PCR, whereas drying of acidified doughs reduced the detectable cell counts by approximately 5 (spray dried) and 2 (roller dried) orders of magnitudes. Incubation of acidified doughs for 24 h did not affect the detectability of LAB cells in spray-dried doughs but further reduced the detectable cell counts in roller-dried doughs by additional 2 orders of magnitude.     

Influence of different storage conditions on changes in the key aroma compounds of orange juice reconstituted from concentrate

Quantification of aroma compounds in an orange juice reconstituted from concentrate which had been stored at 37 °C for 4 weeks (forced storage) revealed an increase in the concentrations of, in particular, dimethyl sulphide, 2-methoxy-4-vinylphenol, α-terpineol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF) in comparison with the same orange juice before storage. On the other hand, clearly lower concentrations were found for octanal, decanal, (R)-α-pinene, linalool, and (E)-β-damascenone after storage, while the concentrations of vanillin and carvone remained nearly constant. Similar results were found for the same aroma compounds after storage of the orange juice at 20 °C for 1 year. Sensory experiments corroborated the importance of 2-methoxy-4-vinylphenol and dimethyl sulphide for the typical stale off-flavour of the stored orange juice, while the omission of e.g., α-terpineol in model mixtures could not be detected. Under both storage conditions (37 °C for 4 weeks or 20 °C for 1 year), the breakthrough odour thresholds of α-terpineol and 4-HDF were not reached, while the concentrations of dimethyl sulphide and 2-methoxy-4-vinylphenol clearly exceeded their breakthrough odour thresholds, thus confirming the crucial role of these odorants for the off-flavour of stored orange juice from concentrate. In addition, changes in the concentrations of selected orange juice odorants at various temperatures and times were investigated.     

Impact of enzymatic mash maceration and storage on anthocyanin and color retention of pasteurized strawberry purées

Strawberry purées were prepared using a commercial polygalacturonase (PG) and a highly purified pectinesterase (PE) preparation, respectively. To elucidate the effect of pectin on color stability following enzymatic pulp maceration, pectin composition was studied by isolating and fractionating the alcohol-insoluble residue from the strawberry purées. The purées were stored at +20 and +4 °C in the dark over a period of 24 weeks monitoring the amounts of monomeric and polymeric anthocyanins as well as antioxidant activities (FRAP, TEAC). Individual anthocyanins were analyzed by HPLC–DAD–MS ⁿ , and color measurements were obtained in the CIE L*a*b* system. Pectin composition was significantly modified following enzymatic maceration of the purées. While PG treatment generally resulted in pectin losses, oxalate-soluble pectins were increased in PE-treated purées. After 24 weeks of storage, the best anthocyanin retention was observed in PE-treated purées. Such products also revealed greatest anthocyanin half-life values and lowest proportion of polymeric pigments. Compared to an untreated control, enzymatic purée maceration using the PG was also beneficial for pigment retention, but less effective than PE. In contrast, color and antioxidant activity were independent of both enzymatic treatments. An initial heating step (90 °C, 10 s) for immediate inactivation of native enzymes such as polyphenoloxidases slightly improved pigment stability, while lowered temperature during mash maceration was less effective. However, by far best color and pigment retention were achieved when the purées were stored at 4 °C in the dark.     

Thermal inactivation of strawberry polyphenoloxidase and its impact on anthocyanin and color retention in strawberry (Fragaria x ananassa Duch.) purées

Strawberry (Fragaria x ananassa Duch.) cultivars were screened for their polyphenoloxidase (PPO) activities, and thermal stability of PPO was evaluated in vitro for three cultivars under different time–temperature regimes (60, 75 and 90 °C for 3 and 5 min, respectively). Heating strawberry purées should further elucidate the impact of thermal treatments on strawberry PPO in its natural matrix (‘in situ’ activity). To evaluate the consequences of PPO inactivation on anthocyanin and color stability, the purées were stored for 28 days at +20 °C monitoring the contents of monomeric, polymeric (spectrophotometrically) and individual anthocyanins (HPLC–DAD–MSⁿ) as well as color properties (CIE L*a*b*). Antioxidant activities (FRAP), total phenolic (Folin–Ciocalteu) and ascorbic acid contents of freshly prepared and stored purées, respectively, were determined spectrophotometrically. PPO activities varied considerably among the cultivars investigated. Accordingly, different time–temperature regimes were required for their complete in vitro and in situ inactivation. Unexpectedly, thermal inactivation of PPO was disadvantageous regarding pigment and color retention of strawberry purées, which was ascribed to partial regeneration of PPO. Hence, protection of antioxidants, total phenolics and ascorbic acid from oxidative degradation could not be achieved by heating the purées prior to storage.     

Occurrence of ochratoxin A in cocoa by-products and determination of its reduction during chocolate manufacture

This work reports an investigation carried out to assess the natural occurrence of ochratoxin A in 168 samples from different fractions obtained during the technological processing of cocoa (shell, nibs, liquor, butter, cake and cocoa powder) and the reduction of ochratoxin A during chocolate manufacture. Ochratoxin A analyses were performed with immunoaffinity columns and detection by high performance liquid chromatography. Concerning the natural ochratoxin A contamination in cocoa by-products, the highest levels of ochratoxin A were found in the shell, cocoa powder and cocoa cake. The cocoa butter was the least contaminated, showing that ochratoxin A seems to remain in the defatted cocoa solids. Under the technological conditions applied during the manufacture of chocolate in this study and the level of contamination present in the cocoa beans, this experiment demonstrated that 93.6% of ochratoxin A present in the beans was reduced during the chocolate producing.     

Miniaturization limits for single-chamber micro-solid oxide fuel cells with coplanar electrodes

Single-chamber solid oxide fuel cells with coplanar microelectrodes were operated in methane–air mixtures (R_mix = 2) at 700 °C. The performance of cells with one pair of NiO–YSZ (yttria stabilized zirconia) anode and (La_0.8Sr_0.2)_0.98MnO₃–YSZ cathode, arranged parallel on a YSZ electrolyte substrate, was found to be significantly dependent on the electrode width. For an interelectrode gap of 250 μm, cells with average electrode widths exceeding 850 μm could establish a stable open circuit voltage (OCV) of 0.8 V, while those with widths less than 550 μm could not establish any OCV. In the intermediate range, the cells exhibited significant fluctuations in voltage and power under our testing conditions. This behavior suggests that a lower limit to electrode dimensions exists for cells with single electrode pairs, below which neither a stable difference in oxygen partial pressure, nor an OCV, can be established. Conversely, increasing the electrode width imposes a penalty in the form of an increase in the cell resistance. However, both size limits can be circumvented by employing multiple pairs of microscale electrodes in an interdigitated configuration.     

Performance evaluation of a.c. and d.c. direct coupled photovoltaic water pumping systems

Photovoltaic (PV) water pumping systems have been widely tested and assessed in Indonesia because of the deficiency of potable water in remote areas. Several different PV water pumping systems, such as a.c./d.c. with/without battery and various pumps, have been tested in the field. Further study, evaluation and classification of optimized PV water pumping systems is needed. Three of those pumping systems were installed in Sumba Island in 1983, in three adjacent villages with similar climate and environment conditions. Two of the installations had a.c. direct coupled systems and the other had d.c. The a.c. systems used a 3.65 kW_p PV generator each and the d.c. system used 5.76 kW_p. After comparing the performance data of both systems, it can be concluded that the a.c. system performs better and needs less maintenance on the pump. In May 1987, as a result of this evaluation, the 5.76 kW_p d.c. system was replaced by an a.c. one, and its capacity was increased to 9.22 kW_p. Meanwhile, the 3.65 kW_p a.c. system was increased to 3.88 kW_p.     

Evidence for a transitional period for development of persistence in infant rats.

Conducted 4 experiments with a total of 188 rat pups to test the hypothesis that rat pups can learn persistence at age 11 days but cannot express this learning in their behavior until they are a few days older. Exp I used a space-trial procedure to investigate the relative reinforcing effects of milk suckling, dry suckling, and contact without suckling at ages 11 and 14 days. Exp II used the Exp I procedure, manipulating schedule of reward at 2 ages and under 2 of the reward conditions. Exp III manipulated the dry suckling reward schedule in 11- and 14-day-old pups. Exp IV manipulated partial and continuous reinforcement on Day 11 but tested for persistence on Day 14. Results suggest the existence of a traditional period in neonatal rats for the learning of persistence. Partial reinforcement training with suckling on an anesthetized dam as reward induced greater persistence in extinction of the approach response than did continuous reinforcement in rat pups 14 days old but not in 11-day-old pups. Other aspects of this period of development are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)