A magnetic microchip for controlled transport of attomole levels of proteins.

A novel method of controlled transport of proteins immobilized on micrometre-sized magnetic beads in a lab-on-a-chip environment is presented. Bead motion is controlled by lithographically made magnetic elements forming transportation lines in combination with an applied in-plane rotating magnetic field. In this way, transport of attomole amounts of proteins is controlled with micrometre precision. Also, the activity of proteins immobilized on the beads is demonstrated by injecting antibodies into the system. A critical step in developing the method was to reduce sticking forces between beads and substrate during transportation of proteins. Charge interaction was found to be of minor importance compared to hydrophobic forces. To achieve a reliable transport of biologically active proteins, both substrate and beads were coated with polyethylene glycol (PEG) and the protein covered beads were suspended in buffer with surfactants. The described system fulfils all the important unit operations of a microfluidic platform and, as a further advantage, presents less need for microchannels and electric wiring.

A structure-activity study of nociceptin-(1-13)-peptide amide. Synthesis of analogues substituted in positions 0, 1, 3, 4 and 10.

A series of analogues of nociceptin, Noc(1-13)NH(2) (an agonist at the ORL1 receptor) was synthesized with following modifications: (1) N-terminal extension with Arg(0); (2) replacement of Gly(3) by basic or polar amino acids-Arg, Asn, Lys(For) or deletion; (3) exchange of Phe(1) or Phe(4) by Phe(NO(2)); (4) substitution of Ser(10) with D-Ser, Pro, D-Pro. The analogs were synthesized by solid-phase methodology using Fmoc-amino acid pentafluorophenyl esters. The affinity for the ORL1 and for the kappa, micro and delta-opioid receptors was investigated by radioligand binding assay and bioactivity by a mouse vas deferens (MVD) assay. The addition of the amino acid residue Arg to the N-terminal enhances the opioid receptor affinity of Noc(1-13)NH(2) while retaining ORL1 receptor affinity at a moderate level. The replacement of Gly in position 3 by the basic or polar amino acids-Arg, Asn, Lys(For) or its deletion led to inactive analogues. The replacement of Ser in position 10 by its D-isomer, Pro and D-Pro resulted in a series of analogues with the following order of activity: Ser(10)>D-Ser(10)>Pro(10)>D-Pro(10). In [D-Ser(10)]Noc(1-13)NH(2), introduction of an additional Phe(NO(2))(4) led to a >60-fold increase of ORL1 affinity, completely attenuating the loss of affinity brought about by Ser(10). In other analogues, introduction of Phe(NO(2))(4) did not change the magnitude of ORL1 binding significantly. Generally, while modifications in position 3 frequently led to a loss of most or all bioactivity, modifications in position 0 (Arg(0)) or 4 (Phe(NO(2))(4)) and 10 (D-Ser(10), Pro(10)) are tolerated.

Determination of conductivity of bacteria by using cross-flow filtration.

An important property of the bacterial surface is its conductivity. To obtain reliable conductivity values, it is essential to handle the cells as gently as possible during the measurement procedure. We have developed a method where a standard conductivity meter is used in combination with cross-flow filtration, thus avoiding repeated centrifugation and resuspension. With this method, the conductivity of Bacillus subtilis was determined to be 7,000 microS/cm, which is a deviation from previously published data by almost an order of a magnitude.