Into the first biomimetic sphingomyelin stationary phase: Suitability in drugs' biopharmaceutic profiling and block relevance analysis of selectivity.

STATE OF THE ART: Sphingomyelin (SPH) is a type of sphingolipid found in animal nerve tissues, especially in the membranous myelin sheath that surrounds some nerve cell axons. Because of its characteristics, SPH stationary phase represents an ideal tool to mimic the interactions taking place between active pharmaceutical ingredients and neurons. METHOD: The IAM.SPH stationary phase (0.821 mg) was suspended in methanol (7.0 mL) and the resulting slurry packed (600 bar) in an HPLC column (10 cm x 2.1 mm). The column was operated at 300 µL min-1 at 25°C using a mobile phase consisting of 60/25/15 (v/v/v) Dulbecco's phosphate buffer saline pH 7.4/methanol/acetonitrile. The elution was achieved isocratically and monitored by UV detection at 220 nm. The investigated dataset consisted of 88 compounds (36 neutrals, 26 bases and 26 acids). The block relevance (BR) analysis was accomplished starting by calculating 82 descriptors using the software VS+ and submitting the data matrices to Matlab. Multiple linear regression and related descriptors were obtained with Vega ZZ 64. RESULTS AND DISCUSSION: The method developed allowed to achieve a solid and reproducible SPH affinity scale for the assayed compounds. Computational studies produced statistically significant models for the prediction and mechanism elucidation of the retentive behavior of pharmaceutically relevant compounds on the SPH stationary phase. CONCLUSIONS: For ionizable compounds, the IAM.SPH exhibited an original selectivity when compared to the commercially available IAM.PC. Moreover, apart from its suitability to surrogate log BB, IAM.SPH was also found relate significantly with the drugs' fraction unbound in plasma, a crucial parameter in pharmacokinetics.

Untapped Opportunities of Resin-to-Resin Transfer Reactions (RRTR) for the Convergent Assembly of Multivalent Peptide Conjugates.

Handling of the individual fragments remains a bottleneck in the convergent assembly of peptides. Overlooked since the emergence of ligation chemistries during the past two decades, so-called resin-to-resin transfer reactions (RRTR) are here described as a strategic shortcut in this context. Condensation of the involved moieties at an acceptor resin is facilitated by shuttling peptide segments directly from a donor resin in a one-pot fashion. The straightforward synthesis of a sterically constrained 13-mer peptidosteroid model illustrates the utility of this approach, presenting the first successful application of the RRTR methodology in the field of multivalent design and bioconjugation. Relying on established procedures to generate, monitor and isolate intermediates and products, the solid-phase nature of the entire strategy allows for the fast construction of polypeptide adducts and libraries thereof. As such, a rejuvenated use and new opportunities for RRTR are reported.

Evaluation of sphingomyelin, cholester, and phosphatidylcholine-based immobilized artificial membrane liquid chromatography to predict drug penetration across the blood-brain barrier.

Over the past decades, several in vitro methods have been tested for their ability to predict drug penetration across the blood-brain barrier. So far, in high-performance liquid chromatography, most attention has been paid to micellar liquid chromatography and immobilized artificial membrane (IAM) LC. IAMLC has been described as a viable approach, since the stationary phase emulates the lipid environment of a cell membrane. However, research in IAMLC has almost exclusively been limited to phosphatidylcholine (PC)-based stationary phases, even though PC is only one of the lipids present in cell membranes. In this article, sphingomyelin and cholester stationary phases have been tested for the first time towards their ability to predict drug penetration across the blood-brain barrier. Upon comparison with the PC stationary phase, the sphingomyelin- and cholester-based columns depict similar predictive performance. Combining data from the different stationary phases did not lead to improvements of the models.

Patchwork protein chemistry: a practitioner's treatise on the advances in synthetic peptide stitchery.

With the study of peptides and proteins at the heart of many scientific endeavors, the omics era heralded a multitude of opportunities for chemists and biologists alike. Across the interface with life sciences, peptide chemistry plays an indispensable role, and progress made over the past decades now allows proteins to be treated as molecular patchworks stitched together through synthetic tailoring. The continuous elaboration of sophisticated strategies notwithstanding, Merrifield's solid-phase methodology remains a cornerstone of chemical protein design. Although the non-practitioner might misjudge peptide synthesis as trivial, routine, or dull given its long history, we comment here on its many advances, obstacles, and prospects from a practitioner's point of view. While sharing our perspectives through thematic highlights across the literature, this treatise provides an interpretive overview as a guide to novices, and a recap for specialists.

Inactivated virus vaccines from chemistry to prophylaxis: merits, risks and challenges.

The aim of this review is to make researchers aware of the benefits of an efficient quality control system for prediction of a developed vaccine's efficacy. Two major goals should be addressed when inactivating a virus for vaccine purposes: first, the infectious virus should be inactivated completely in order to be safe, and second, the viral epitopes important for the induction of protective immunity should be conserved after inactivation in order to have an antigen of high quality. Therefore, some problems associated with the virus inactivation process, such as virus aggregate formation, protein crosslinking, protein denaturation and degradation should be addressed before testing an inactivated vaccine in vivo.

Development of the first sphingomyelin biomimetic stationary phase for immobilized artificial membrane (IAM) chromatography.

A prototype sphingomyelin stationary phase for Immobilized Artificial Membrane (IAM) chromatography was synthesized by an ultra-short, solid-phase inspired methodology, in which an oxidative release monitoring strategy played a vital role. Evaluated in a proof-of-concept model for blood-brain barrier passage, partial least squares regression demonstrated its potential as an in vitro prediction tool.

Shortcut access to peptidosteroid conjugates: building blocks for solid-phase bile acid scaffold decoration by convergent ligation.

We present three versatile solid-supported scaffold building blocks based on the (deoxy)cholic acid framework and decorated with handles for further derivatization by modern ligation techniques such as click chemistry, Staudinger ligation or native chemical ligation. Straightforward procedures are presented for the synthesis and analysis of the steroid constructs. These building blocks offer a new, facile and shorter access route to bile acid-peptide conjugates on solid-phase with emphasis on heterodipodal conjugates with defined spatial arrangements. As such, we provide versatile new synthons to the toolbox for bile acid decoration.