Stable and Selective Formation of Hoogsteen-Type Triplexes and Duplexes Using Twisted Intercalating Nucleic Acids (TINA) Prepared via Postsynthetic Sonogashira Solid-Phase Coupling Reactions

2005 ◽  
Vol 127 (42) ◽  
pp. 14849-14858 ◽  
Author(s):  
Vyacheslav V. Filichev ◽  
Erik B. Pedersen
Keyword(s):  
Nucleic Acids ◽  
Solid Phase ◽  
Coupling Reactions ◽  
Phase Coupling ◽  
Selective Formation

Purification of large peptides using Chemoselective tags

1999 ◽  
Author(s):  
Paolo Mascagni
Keyword(s):  
Amino Acid ◽  
Synthetic Peptides ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Exchange Chromatography ◽  
Target Sequence ◽  
Coupling Reactions ◽  
Amino Acid Residues ◽  
Quaternary Structures ◽  
Specific Stationary Phase

In solid phase peptide synthesis (SPPS), deletion sequences are generated at each addition of amino acid due to non-quantitative coupling reactions. Their concentration increases exponentially with the length of the peptide chain, and after many cycles not only do they represent a large proportion of the crude preparation, but they can also exhibit physicochemical characteristics similar to the target sequence. Thus, these deletion-sequence contaminants present major problems for removal, or even detection. In general, purification of synthetic peptides by conventional chromatography is based on hydrophobicity differences (using RP-HPLC) and charge differences (using ion-exchange chromatography). For short sequences, the use of one or both techniques is in general sufficient to obtain a product with high purity. However, on increasing the number of amino acid residues, the peptide secondary and progressively tertiary and quaternary structures begin to play an important role and the conformation of the largest peptides can decisively affect their retention behaviour. Furthermore, very closely related impurities such as deletion sequences lacking one or few residues can be chromatographically indistinguishable from the target sequence. Therefore, purification of large synthetic peptides is a complex and time-consuming task that requires the use of several separation techniques with the inevitable dramatic reduction in yields of the final material. Permanent termination (capping) of unreacted chains using a large excess of an acylating agent after each coupling step prevents the formation of deletion sequences and generates N-truncated peptides. However, even under these more favourable conditions, separation of the target sequence from chromatographically similar N-capped polypeptides requires extensive purification. If the target sequence could be specifically and transiently labelled so that the resulting product were selectively recognized by a specific stationary phase, then separation from impurities should be facilitated. This chapter deals with such an approach and in particular with the purification of large polypeptides, assembled by solid phase strategy, using lipophilic and biotin-based 9-fluorenylmethoxycarbonyl (Fmoc) chromatographic probes. Assuming that the formation of deletion sequences is prevented by capping unreacted chains, a reciprocal strategy can be applied that involves functional protection of all polymer-supported peptide chains that are still growing, with a specially chosen affinity reagent or chromatographic probe.

Introduction — a retrospective viewpoint

1999 ◽  
Author(s):  
R. C. Sheppard
Keyword(s):  
Peptide Synthesis ◽  
Solid Phase ◽  
Chemical Society ◽  
Benzyl Ester ◽  
Heterogeneous Reactions ◽  
New Technique ◽  
Annual Reports ◽  
Coupling Reactions ◽  
Peptide Chemistry ◽  
The Difference

The Chemical Society publication Annual Reports on the Progress of Chemistry for 1963 attempted to inform readers of all the highly significant advances in all the major fields of pure chemistry during that year. Fortunately, the section on peptide chemistry drew attention to a paper by R. B. Merrifield which had just been published in the Journal of the American Chemical Society: A novel approach to peptide synthesis has been the use of a chloromethylated polystyrene polymer as an insoluble but porous solid phase on which the coupling reactions are carried out. Attachment to the polymer constitutes protection of the carboxyl group (as a modified benzyl ester), and the peptide is lengthened from its amino-end by successive carbodiimide couplings. The method has been applied to the synthesis of a tetrapeptide, but incomplete reactions lead to the accumulation of by products. Further development of this interesting method is awaited. I remember thinking at the time that in this paper we had possibly seen both the beginning and the end of the interesting new technique of solid phase peptide synthesis. To many organic chemists, the described result was that anticipated—difficulty in bringing heterogeneous reactions to completion resulting in impure products. Both this and purification problems were expected to worsen as the chain length was increased beyond Merrifield’s tetrapeptide limit. In fact, I probably had at the time an inadequate appreciation of the difference between truly heterogeneous or surface reactions and those in the solvated gel phase. The latter approaches much more closely the solution situation. However, the new technique also flouted many of the basic principles of contemporary organic synthesis which required rigorous isolation, purification, and characterization regimes following each synthetic step. In Merrifield’s new technique, isolation consisted simply of washing the solid resin, there was no other purification of the products of each reaction, and little or no characterization of resin-bound intermediates was attempted. The first two of these are of course the important characteristics which give the method its speed and simplicity and contribute to its efficiency. Small wonder, though, that in many minds there was doubt about the future of the new technique.

ChemInform Abstract: SOLID-PHASE COUPLING OF ARGINYL-PEPTIDES

1977 ◽  
Vol 8 (29) ◽  
pp. no-no
Author(s):  
C. DI BELLO ◽  
A. MARIGO ◽  
O. BUSO ◽  
A. LUCCHIARI
Keyword(s):  
Solid Phase ◽  
Phase Coupling

scholarly journals Solid phase selective separation and green preconcentration of Cu, Zn, Pb and Cd in drinking water by using novel functionalized resin

2009 ◽  
Vol 7 (4) ◽  
pp. 945-954 ◽  
Author(s):  
Nagwa Burham ◽  
Sami Azeem ◽  
Mohamed El-Shahat
Keyword(s):  
Drinking Water ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Exchange Capacity ◽  
Coupling Reactions ◽  
Lead And Cadmium ◽  
Sample Flow Rate ◽  
Relative Standard ◽  
Copper Zinc ◽  
Ph Range

AbstractA new solid — phase extraction sorbent was developed based on stepwise anchoring of two ligand molecules for the determination of copper, zinc, lead and cadmium in drinking water by flame AAS. Amberlite XAD-2 functionalized with 4′-(2-hydroxyphenylazo)-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one (HPAPyr) was utilized for preconcentration/separation of these elements. The sorbent was prepared by two successive azo coupling reactions. First, 2-aminophenol was anchored to the amino groups in the resin resulted from nitration followed by reduction. Then, the resulted 2-aminophenol functionalized resin was further diazotized and coupled to the pyrazolone compound and the final product HPAPyr-XAD-2 was characterized by IR and elemental analysis. The optimum pH range for sorption, shaking time, exchange capacity, sample flow rate, preconcentration factor and interference from co-existing ions were investigated. All metal ions were quantitatively desorbed from the resin by 4.5 mol L−1 nitric acid solution. The sorbent provides limit of detection within the range 0.9–3.3 µg L−1 and concentration factor up to 250. The procedure was validated by analysis of certified material NIST-SRM 1577b. Application to drinking water showed satisfactory results with relative standard deviation RSD ≤ 8.5%.

Solid-phase Suzuki cross-coupling reactions using a phosphine ligand based on a phospha-adamantane framework

2004 ◽  
Vol 45 (29) ◽  
pp. 5661-5663 ◽  
Author(s):  
Stephan A. Ohnmacht ◽  
Tim Brenstrum ◽  
Konrad H. Bleicher ◽  
James McNulty ◽  
Alfredo Capretta
Keyword(s):  
Solid Phase ◽  
Cross Coupling ◽  
Phosphine Ligand ◽  
Coupling Reactions ◽  
Cross Coupling Reactions
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