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Hedi Raizer

Journal 3 min read

Which peptides are studied in relation to solid-phase peptide synthesis?

Solid-phase peptide synthesis (SPPS) is the dominant method for assembling peptides on a resin support. This page surveys the peptides and peptide classes that appear in the SPPS literature, including LL-37 analogues, D-

peptides-pro Editorial

Solid-phase peptide synthesis (SPPS) is the stepwise assembly of a peptide chain while it is anchored to an insoluble polymeric support. The peptide classes studied in relation to SPPS include host-defence cathelicidins and their analogues, D-amino-acid-containing sequences, and short to medium-length sequences synthesised on alternative supports such as non-swelling silica. The evidence block for this page covers three areas: LL-37 analogues built from 2,3-diaminopropionic acid building blocks with an oxa-acid spacer [1], FDA-approved drugs containing D-amino acids [2], and silica-assisted solid-phase peptide synthesis (SiPPS) [3].

Human cathelicidin LL-37 is a 37-residue peptide with a net charge of +6. It couples broad-spectrum antimicrobial activity with immunomodulatory function, and its therapeutic use is limited by rapid proteolysis and by peptidylarginine deiminase (PAD)-mediated citrullination [1]. The work centres on the immunomodulatory and antimicrobial functions of the cathelicidin family, and on the enzymatic stability of the peptide backbone.

Research Studies

LL-37 analogues and enzymatic stability

LL-37 is a 37-residue human cathelicidin with a net charge of +6. Its therapeutic use is limited by rapid proteolysis and by PAD-mediated citrullination [1]. Analogues built from 2,3-diaminopropionic acid functionalised with an oxa-acid spacer were studied for their effect on enzymatic stability and on neutrophil degranulation. The reported outcome was enhanced enzymatic stability and selective suppression of neutrophil degranulation [1]. This is an in vitro / biochemical finding; no human dosing or clinical outcome is reported in the evidence block.

D-amino acids and proteolytic resistance

D-amino acids are the non-natural enantiomers of L-amino acids. They are used in peptide drug development because of resistance to proteolytic degradation, enhanced conformational rigidity, and reduced immunogenicity [2]. These properties make them valuable in designing long-acting peptides. The evidence block describes a historical and developmental perspective on FDA-approved drugs containing D-amino acids [2].

Silica-assisted solid-phase peptide synthesis (SiPPS)

SiPPS uses a non-swelling silica-based resin for peptide synthesis. The strategy is similar to that of conventional SPPS. In the reported work, a 2-hour coupling seemed to favour coupling compared with a 1-hour standard coupling [3]. The use of this non-swelling support is the distinguishing feature of the method.

Comparison of coupling times in SiPPS

Coupling conditionReported observation
1-hour standard couplingReference condition
2-hour couplingSeemed to favour coupling compared with 1-hour standard coupling [3]

LL-37 and PAD-mediated citrullination

LL-37 is subject to PAD-mediated citrullination, which together with rapid proteolysis limits its therapeutic use [1]. Analogues modified with 2,3-diaminopropionic acid building blocks and an oxa-acid spacer were studied in relation to this limitation, with the reported outcome of enhanced enzymatic stability [1].

D-amino-acid-containing FDA-approved drugs

The evidence block reports a historical and developmental perspective on FDA-approved drugs containing D-amino acids [2]. The properties cited for D-amino acids in this context are resistance to proteolytic degradation, enhanced conformational rigidity, and reduced immunogenicity [2].

Non-swelling silica resin in peptide synthesis

SiPPS uses a non-swelling silica-based resin. The strategy is similar to that of SPPS, and a 2-hour coupling seemed to favour coupling compared with a 1-hour standard coupling [3]. The evidence block does not report sequence, yield, or purity values for specific peptides made by SiPPS.

LL-37 and neutrophil degranulation

LL-37 analogues built from 2,3-diaminopropionic acid functionalised with an oxa-acid spacer were reported to produce selective suppression of neutrophil degranulation, alongside enhanced enzymatic stability [1]. This is an in vitro finding; the evidence block does not report an animal model or a human study for this effect.

If you are reading this for personal health reasons

The materials described on this page are sold for laboratory research only. We do not provide dosing, medical guidance, or recommendations for personal use. Anyone considering a compound for themselves should speak to a licensed clinician.

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