Modulating Secondary Structure Motifs Through Photo-Labile Peptide Staples.

Peptide-protein interactions (PPIs) are facilitated by the well-defined three-dimensional structure of bioactive peptides, interesting compounds for the development of new therapeutic agents. Their secondary structure and thus their propensity to engage in PPIs can be influenced by the introduction of peptide staples on the side chains. In particular, light-controlled staples based on azobenzene photoswitches and their structural influence on helical peptides have been studied extensively. In contrast, photolabile staples bearing photocages as a structural key motif, have mainly been used to block supramolecular interactions. Their influence on the secondary structure of the target peptide is under-investigated. Thus, in this study we use a combination of spectroscopic techniques and in silico simulations to systematically study a series of helical peptides with varying length of the photo-labile staple to obtain a detailed insight into the structure-property relationship in such photoresponsive biomolecules.

Artificial peptides to induce membrane denaturation and disruption and modulate membrane composition and fusion.

Membranes consisting of phospholipid bilayers are an essential constituent of eukaryotic cells and their compartments. The alteration of their composition, structure, and morphology plays an important role in modulating physiological processes, such as transport of molecules, cell migration, or signaling, but it can also lead to lethal effects. The three main classes of membrane-active peptides that are responsible for inducing such alterations are cell-penetrating peptides (CPPs), antimicrobial peptides (AMPs), and fusion peptides (FPs). These peptides are able to interact with lipid bilayers in highly specific and tightly regulated manners. They can either penetrate the membrane, inducing nondestructive, transient alterations, or disrupt, permeabilize, or translocate through it, or induce membrane fusion by generating attractive forces between two bilayers. Because of these properties, membrane-active peptides have attracted the attention of the pharmaceutical industry, and naturally occurring bioactive structures have been used as a platform for synthetic modification and the development of artificial analogs with optimized therapeutic properties to transport biologically active cargos or serve as novel antimicrobial agents. In this review, we focus on synthetic membrane interacting peptides with bioactivity comparable with their natural counterparts and describe their mechanism of action.

Tear osmolarity after cataract surgery.

PURPOSE: To evaluate the changes in tear film osmolarity and Schirmer I test after cataract surgery. METHODS: This single-center, prospective study included patients with no subjective complaints about dry eye disease. Patients with the following conditions were excluded: contact lens wearers, patients with diabetes, pseudoexfoliation, pterygia, and eye drops users. The eye that had not undergone surgery was considered the control group. Tear osmolarity and Schirmer I test were evaluated before surgery and during the first postoperative month. RESULTS: Thirty-seven patients were enrolled in the study. Before surgery, tear osmolarity was 301.2 ± 15.09 Osm/L in the study group and 302.3 ± 14.21 mOsm/L in the control group (P = 0.2), while Schirmer I test averaged 13.4 ± 10.50 mm in the study group and 13.7 ± 10.79 mm in the control group (P = 0.6). The next morning, the tear osmolarity decreased to <275 mOsm/L in the study group while in the control group, the value increased to 303.1 mOsm/L ± 13.68 (P = 0.008). The Schirmer I test in the same morning showed an increase up to 19.9 ± 9.73 mm in the study group and to 15.7 ± 10.19 mm in the control group (P = 0.01). One week later, the tear osmolarity increased to 311.8 ± 14.85 mOsm/L, while the control group averaged 301.7 ± 11.84 mOsm/L (P = 0.013). The Schirmer I test results decreased to 15.8 ± 9.37 mm in the study group and 13.9 ± 10.19 mm in the control group (P = 0.07) one week after the surgery. One month after surgery, tear osmolarity and Schirmer I test results in the study group decreased to the control group level (P > 0.05). CONCLUSIONS: The tear osmolarity results increased to the dry eye disease level in the first postoperative week. Over the course of one month, the difference in tear osmolarity and Schirmer I test values for the study and control groups leveled off.