4 research outputs found
Thermal cleavage of the Fmoc protection group
The Fmoc protection group is among the most commonly used protection groups for the amino function. A fast method for the thermal deavage of this protection group under base-free conditions without the need for dibenzofulvene scavengers is presented. The advantages of this method include straightforward testability by means of a simple high-temperature NMR experiment, usually high yields, and good selectivity towards the BOC protection group and t-butyl ethers
Squaraine Planar-Heterojunction Solar Cells
The photovoltaic performance of squaraine-based organic solar cells is investigated. Two squaraine derivatives with extraordinarily high extinction coefficients are used as electron donors in bilayer heterojunctions with fullerene as electron acceptor. Due to the very strong squaraine absorption band in the red spectral domain, antibatic behavior due to light filtering is observed in the photocurrent spectrum for film thicknesses of 35 nm to 40 nm. At reduced film thicknesses of 20 nm, this filtering effect at maximum absorption can be alleviated and power conversion efficiencies under simulated AM 1.5 full sun irradiation of 0.59% and 1.01% are obtained for the two squaraine derivatives, respectively. The photovoltaic properties of these cells are investigated with respect to electrode materials and chemical doping.ISSN:1110-662XISSN:1687-529
The effect of agaricus brasiliensis extract supplementation on honey bee colonies
This study was done to discover any beneficial effect of a medicinal mushroom Agaricus brasiliensis extract on the honey bee. Firstly, a laboratory experiment was conducted on 640 bees reared in 32 singleuse plastic rearing cups. A. brasiliensis extract proved safe in all doses tested (50, 100 and 150 mg/kg/ day) irrespective of feeding mode (sugar syrup or candy). Secondly, a three-year field experiment was conducted on 26 colonies treated with a single dose of A. brasiliensis extract (100 mg/kg/day) added to syrup. Each year the colonies were treated once in autumn and twice in spring. The treatments significantly increased colony strength parameters: brood rearing improvement and adult population growth were noticed more often than the increase in honey production and pollen reserves. These positive effects were mainly observed in April. In conclusion, A. brasiliensis extract is safe for the bees and helps maintaining strong colonies, especially in spring.</p
Quantitative Assessment of Preloaded 4‑Alkoxybenzyl Alcohol Resins for Solid-Phase Peptide Syntheses by 1D and 2D HR-MAS NMR
The quality of preloaded Wang resins is very important
for the
success of solid-phase peptide syntheses (SPPS). A critical factor
is the capping of remaining hydroxyl groups after loading with the
first amino acid, since these free alcohols lead to truncated sequences
during the following SPPS steps. Because the detection of hydroxyl
groups by color tests is difficult and unreliable, the capping efficiency
is often controlled by time-consuming peptide test syntheses. Here,
we describe a two-dimensional, high resolution magic angle spinning
NMR method for the quantitative determination of remaining 4-alkoxybenzyl
alcohols in Fmoc-Xaa-Wang resins with a detection limit of 1 mol-%.
The NMR method was validated with samples of known ratios between
Fmoc-Ala-Wang and 4-alkoxybenzylalcohol resin. Application to a set
of preloaded Fmoc-Ala- and Fmoc-ThrÂ(tBu)-Wang test resins demonstrated
that the full range of essential amino acids can be quantified without
further spectrometer calibration. Compared to established test synthesis
protocols, the NMR method represents not only advantages in terms
of time and cost savings but also eliminates all inaccuracies due
to further sample treatment like SPPS and cleavage from the resin