These positively charged, amphipathic peptides were termed cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) [11–13]. Among synthetic peptides, the cellular uptake of polyarginine was found to be much more efficient than that of polylysine, polyhistidine, or polyornithine [13, 14]. We found that a nona-arginine (R9) CPP peptide can enter cells by itself or in conjunction with an associated cargo [15–21]. Cargoes that R9 can carry include proteins, DNAs, RNAs, and inorganic nanoparticles (notably, quantum dots; QDs). R9 can form complexes with cargoes in covalent, noncovalent, or mixed covalent and noncovalent manners [22–24]. BIIB057 clinical trial CPPs can deliver cargoes up to 200 nm in diameter

[11, 25], and R9 can internalize into cells of various species, including mammalian cells/tissues, plant cells, bacteria, protozoa, and arthropod cells [16, 17, 26, 27]. Despite many studies using various biological and biophysical techniques, our understanding of the https://www.selleckchem.com/products/KU-55933.html mechanism of CPP selleck inhibitor entry remains incomplete and somewhat controversial. Studies have indicated that CPPs enter cells by energy-independent and energy-dependent pathways [28]. The concentration of CPPs appears to influence the mechanism of cellular uptake [28]. Our previous

studies indicated that macropinocytosis is the major route for the entry of R9 carrying protein or DNA cargoes associated in a noncovalent fashion [15, 29, 30]. However, we found that CPP/QD complexes enter cells by multiple pathways [31, 32]. Multiple pathways of cellular uptake were also demonstrated with CPP-fusion protein/cargo complexes associated in a mixed covalent and noncovalent manner [22, 24]. In contrast, our study of the R9 modified with polyhistidine (HR9) indicated direct membrane translocation [33]. The cellular entry mechanisms of CPPs in

cyanobacteria Vorinostat have not been studied. In the present study, we determined CPP-mediated transduction efficiency and internalization mechanisms in cyanobacteria using a combination of biological and biophysical methods. Results Autofluorescence To detect autofluorescence in cyanobacteria, either live or methanol-killed cells were observed using a fluorescent microscope. Both 6803 and 7942 strains of cyanobacteria emitted red fluorescence under blue or green light stimulation (Figure 1, left panel) when alive; dead cells did not display any fluorescence (Figure 1, right panel). This phenomenon was confirmed using a confocal microscope; dead cyanobacteria treated with either methanol or killed by autoclaving emitted no red fluorescence (data not shown). Thus, red autofluorescence from cyanobacteria provided a unique character. Figure 1 Autofluorescence detection in 6803 and 7942 strains of cyanobacteria. Cells were treated with either BG-11 medium or 100% methanol to cause cell death. Bright-field and fluorescent images in the RFP channel were used to determine cell morphology and autofluorescence, respectively.