1. Detection of proopiomelanocortin mRNA by in situ hybridization, using a biotinylated oligodeoxynucleotide probe and avidin-alkaline phosphatase histochemistry
T Christensen, H Dalbøge, L I Larsson Histochemistry . 1988;89(2):109-16. doi: 10.1007/BF00489913.
A synthetic 24-mer oligodeoxynucleotide complementary to the region of proopiomelanocortin (POMC) mRNA that codes for the MSH core sequence (alpha MSH/ACTH[4-11]), was synthesized and labelled in the 3'-end by use of terminal transferase. Probes tailed with either [3H]- or biotin-labelled nucleotides could be used for in situ hybridization studies. Biotinylated probes, hybridized to mouse and rat pituitary sections, were detected by avidin-alkaline phosphatase or streptavidin-alkaline phosphatase procedures and development in 5-bromo-4-chloro-3-indolyl phosphate (BCIP)-nitroblue tetrazolium (NBT). Proteinase K pretreatment of sections produced a drastic enhancement of the signal obtained, particularly in strongly fixed, paraffin-embedded material. The non-radioactive in situ hybridization technique compared favourably to radioactive in situ hybridization in terms of rapidity and precision of the localization. Controls involved deletion of the probe to prove that other components of the reaction sequence did not yield stain, digestion with RNase to prove that tissue RNA was necessary to bind the probe, prehybridization (blocking) with unlabelled probe to prove that the biotinylated probe reacted with its anti-sense region and not its tail and Northern blotting to show that the probe reacted with only one species of pituitary RNA, having the size of mouse pituitary POMC mRNA. In addition, adrenalectomy, known to increase anterior lobe POMC levels, resulted in both increased numbers and increased intensity of positive corticotroph-like cells. Synthetic oligodeoxynucleotides labelled with biotin appear to constitute attractive reagents for in situ hybridization studies when supported by appropriate control procedures.
2. Solid phase peptide synthesis on hydrophilic supports. Part II--Studies using Perloza beaded cellulose
D R Harding, D R Englebretsen Int J Pept Protein Res . 1992 Dec;40(6):487-96.
Beaded cellulose (Perloza) was modified with acrylonitrile followed by reduction with diborane to give a functionalised support containing aminopropyl groups. This spacer arm was then further extended with a glycolamido or an Fmoc-amino acid-4-oxymethylphenoxyacetyl moiety. A number of peptides, including the Merrifield test peptide leucyl-alanyl-glycyl-valine, leucine-enkephalin, Acyl Carrier Protein (65-74), angiotensin I and II, ACTH(4-11) and LHRH were synthesised on the aminopropyl beaded cellulose support using modified t-butyloxycarbonyl (Boc) or fluorenylmethoxycarbonyl (Fmoc) synthesis protocols. The peptides were cleaved from the support and further purified.
3. Cleavable ester linked magnetic nanoparticles for labeling of solvent exposed primary amine groups of peptides/proteins
Laura Osorno, Matthew A Tarr, Casey Grimm, Angela Ellender, Ujwal S Patil Data Brief . 2015 Jun 18;4:302-7. doi: 10.1016/j.dib.2015.05.025.
Covalent labeling of solvent exposed amino acid residues using chemical reagents/crosslinkers followed by mass spectrometric analysis can be used to determine the solvent accessible amino acids of a protein. A variety of chemical reagents containing cleavable bonds were developed to label abundantly found lysine residues on the surface of protein. To achieve efficient separation of labeled peptides prior to mass spectrometric analysis, magnetic nanoparticles can be decorated with amino acid reactive functional groups and utilized for quick recovery of labeled peptides. [1] In this work, iron oxide magnetic nanoparticles (Fe3O4 MNPs) were synthesized by thermal decomposition method and coated with silica (SiO2@Fe3O4 MNPs) by reverse micro emulsion approach. The Fe3O4 MNPs and SiO2@Fe3O4 MNPs were characterized by TEM and XRD. The SiO2@Fe3O4 MNPs were further coated with amine groups and conjugated to N-hydroxysuccinimidyl (NHS) ester groups via a cleavable ester bond. Fluorescence based qualitative analysis of ester linked NHS ester modified SiO2@Fe3O4 MNPs was performed to confirm the presence of NHS ester group. The active NHS ester sites on the surface of SiO2@Fe3O4 MNPs were determined by depletion approach and found to be 694 active sites per 1 mg of SiO2@Fe3O4 MNPs. Free amine groups of a small peptide, ACTH (4-11) were labeled by ester linked, NHS ester modified SiO2@Fe3O4 MNPs under physiological conditions. Superparamagnetic nature of SiO2@Fe3O4 MNPs allowed quick and efficient magnetic separation of labeled peptides from the solution. The ester bond was further cleaved to separate labeled peptides followed by mass spectrometric analysis. The ester linked, NHS ester modified SiO2@Fe3O4 MNPs introduced a mass shift of 115.09 Da on amine groups of ACTH (4-11), which was confirmed by mass spectrometry.
