Inge J. Minten

Constrained and UV-activatable cell-penetrating peptides for intracellular delivery of liposomes.

Herein we report on the development of a novel method of constraining a cell-penetrating peptide, which can be used to trigger transport of liposomes into cells upon in this case radiation with UV-light. A cell-penetrating peptide, which was modified on both termini with an alkyl chain, was anchored to the liposomal surface in a constrained and deactivated form. Since one of the two alkyl chains was connected to the peptide via a UV-cleavable linker, disconnection of this alkyl chain upon irradiation led to the exposure of the cell-penetrating peptide, and mediated the transport of the entire liposome particle into cells.

Controlled encapsulation of multiple proteins in virus capsids.

Multiple proteins can be bound within the Cowpea Chlorotic Mottle Virus capsid shell in an efficient and controlled manner by using heterodimeric coiled-coil peptide oligomers. Through genetic modification, these oligomers can be attached to the capsid protein and an enhanced green fluorescent protein (EGFP). In this way, the capsid proteins can be noncovalently bound to EGFP prior to the induction of the capsid assembly. Up to 15 EGFP proteins can be encapsulated per capsid in a controlled and efficient manner.

Virus-like Particles Templated by DNA Micelles: A General Method for Loading Virus Nanocarriers

DNA amphiphile particles template formation of virus capsids and enable their loading.

Designing Two Self-Assembly Mechanisms into One Viral Capsid Protein

ELP-CP, a structural fusion protein of the thermally responsive elastin-like polypeptide (ELP) and a viral capsid protein (CP), was designed, and its assembly properties were investigated. Interestingly, this protein-based block copolymer could be self-assembled via two mechanisms into two different, well-defined nanocapsules: (1) pH-induced assembly yielded 28 nm virus-like particles, and (2) ELP-induced assembly yielded 18 nm virus-like particles. The latter were a result of the emergent properties of the fusion protein. This work shows the feasibility of creating a self-assembly system with new properties by combining two structural protein elements.

Reactions inside nanoscale protein cages

Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in solution, such as vesicles and micelles. The utilization of protein cages as reaction vessels is a relatively new field and very promising as these capsules are inherently monodisperse, in that way providing uniform reaction conditions, and are readily accessible to both chemical and genetic modifications. In this review, we aim to give an overview of the different kinds of nanoscale protein cages that have been employed as confined reaction spaces.

CCMV capsid formation induced by a functional negatively charged polymer

A functional negatively charged polyelectrolyte, polyferrocenylsilane (PFS) was encapsulated in cowpea chlorotic mottle virus (CCMV) capsid proteins, yielding monodisperse particles of 18 nm in size with altered redox properties compared to the parent materials.

Complex Assembly Behavior During the Encapsulation of Green Fluorescent Protein Analogs in Virus Derived Protein Capsules

Enzymes encapsulated in nanocontainers are a better model of the conditions inside a living cell than free enzymes in solution. In a first step toward the encapsulation of multiple enzymes inside the cowpea chlorotic mottle virus (CCMV) capsid, enhanced green fluorescent protein (EGFP) was attached to CCMV capsid proteins. The capsid protein-EGFP complex was then co-assembled with wild-type capsid protein (wt CP) in various ratios. At higher complex to wt CP ratios, the number of EGFP per capsid decreased instead of leveling off. We propose that this unexpected behavior is caused by pH-induced disassembly of the capsid protein-EGFP complex as well as by concentration and ratio dependent dimerization of the complex, making it partially unavailable for incorporation into the capsid.

Disassembling peptide-based fibres by switching the hydrophobic–hydrophilic balance

Amyloid-like model peptides, modified on the N-terminus with an alkyl tail and on the C-terminus with a PEG chain, yielded fibres that were susceptible to triggered disassembly by removal of the alkyl chain, which affected the hydrophobic-hydrophilic balance.

Metal‐Ion‐Induced Formation and Stabilization of Protein Cages Based on the Cowpea Chlorotic Mottle Virus

The cowpea chlorotic mottle virus (CCMV) is a versatile building block for the construction of nanoreactors and functional materials. Upon RNA removal, the capsid can be reversibly assembled and disassembed by adjusting the pH. At pH 5.0 the capsid is in the native assembled conformation, while at pH 7.5 it disassembles into 90 capsid protein dimers. This special property enables the encapsulation of various molecules, such as protein and enzymes, but only at low pH. It is possible to stabilize the capsid at pH 7.5 by addition of negatively charged polyelectrolytes or negatively charged particles, but these methods all fill the interior of the capsid, leaving little or no space for other cargo molecules. This pH restriction therefore severely limits the range of enzymes that can be encapsulated, and hampers the investigation of the CCMV capsid as a nanoreactor for the study of enzymes in confined spaces. Herein, the interaction of N-terminal histidine-tag-modified capsid proteins with several metal ions is reported. Depending on the conditions used, nanometer-sized protein particles or capsidlike architectures are formed that are stable at pH 7.5. This metal-mediated stabilization methodology is employed to form stable capsids containing multiple proteins at pH 7.5, thereby greatly expanding the scope of the CCMV capsid as a nanoreactor.