In this study we describe the use of gold nanoparticles as a fast detection system for the sensitive analysis of proteins. The immunological method allows for protein analysis at the nanogram level, as required for clinical diagnosis. Initially a test protein is used for the development of the assay. The system is subsequently adopted for alpha-fetoprotein, which is a relevant tumor marker. This work demonstrates that antibody functionalized gold nanoparticles can be used for the detection of proteins by forming gold nanoparticle aggregates. The influence of the size of the gold nanoparticles on the sensitivity of the assay is investigated in the range from 20-60 nm particles; the larger particles show here the highest relative changes. The formation of antigen-gold nanoparticle aggregates is detected by an increase in hydrodynamic diameter by dynamic light scattering (DLS). UV/Vis spectroscopy also allows assay monitoring by quantifying the red shift of the plasmon resonance wavelength. Alphafetoprotein can be analysed in the concentration range of 0.1-0.4 mg ml À1 . The influence of pH, ionic strength and ratio of sample to Au-NP solution is studied. With this method, the protein AFP can be rapidly detected as demanded for clinical diagnosis.
meso-Substituted trans-A 2 B 2 -porphyrins bearing specific patterns of substituents are crucial building blocks in porphyrin-based biomimetic systems and molecular materials and can be used for the construction of well-defined porphyrin-based architectures. A new stepwise and rational synthesis of functionalized trans-A 2 B 2 -porphyrins is reported in which for the first time donor-acceptor-substituted cyclopropane precursors (d-a cyclopropanes) are exploited. The three presented d-a cyclopropanes are readily accessible in a multi-gram scale and serve as aldehyde equivalents in the reaction with an excess of pyrrole to afford the corresponding dipyrromethanes (DPMs). The three DPMs were synthesized in yields of 60-74%. They are stable in purified form in the absence of light and air and were subsequently condensed with a wide range of aliphatic and aromatic aldehydes bearing electron-donating or electron-withdrawing substituents followed by oxidation to form the corresponding trans-A 2 B 2 -porphyrins. Fourteen functionalized porphyrins were synthesized in yields of 14-31%, indicating the broad scope of the synthetic procedure. The possibility to introduce key functional groups is emphasized, which enables subsequent modification of these porphyrins with moieties inducing biological activity. Modification of the tetrapyrroles may occur by addition to one of the porphyrin peripheral double bonds, the use of substituents of the aryl groups or via the methoxycarbonyl group at two of the meso-substituents. Three examples of porphyrins were converted into the corresponding 7,8-dihydroxychlorins by osmium-mediated dihydroxylation and one of the resulting chlorins was subjected to saponification to give a highly polar chlorin dicarboxylic acid. A 4-bromophenyl-substituted d-a cyclopropane was prepared by rhodiumcatalyzed cyclopropanation and then transformed into a DPM which was subsequently condensed to a porphyrin. Its Zn complex allowed a Heck reaction to afford the functionalized bisA C H T U N G T R E N N U N G (alkenyl)-substituted trans-A 2 B 2 -Zn-porphyrin.
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