Disassembling ability of lipopeptide promotes the antibacterial activity.

Lipopeptides have become one of the most potent antibacterial agents, however, there is so far no consensus about the link between their physic-chemical properties and biological activity, in particular their inherent aggregation propensity and antibacterial potency. To this end, we here de novo design a series of lipopeptides (CnH(2n-1)O-(VVKK)2V-NH2), in which an alkyl chain is covalently attached onto the N-terminus of a short cationic peptide sequence with an alternating pattern of hydrophobic VV (Val) and positively charged KK (Lys) motifs. By varying the alkyl chain length (ortho-octanoic acid (C8), lauric acid (C12), and palmitic acid (C16)), the lipopeptides show distinct physicochemical properties and self-assembly behaviors, which have great effect on their antibacterial activities. C8H15O-(VVKK)2V-NH2, which contains the lowest hydrophobicity and surface activity has the lowest antibacterial activity. C12H23O-(VVKK)2V-NH2 and C16H31O-(VVKK)2V-NH2 both have high hydrophobicity and surface activity, and self-assembled into long nanofibers. However, the nanofibers formed by C12H23O-(VVKK)2V-NH2 disassembled by dilution, resulting in its high antibacterial activity via bacterial membrane disruption. Comparatively, the nanofibers formed by C16H31O-(VVKK)2V-NH2 were very stable, which can closely attach on bacterial surface but not permeate bacterial membrane, leading to its low antibacterial activity. Thus, the stability other than the morphologies of lipopeptides' nanostructures contribute to their antibacterial ability. Importantly, this study enhances our understanding of the antibacterial mechanisms of self-assembling lipopeptides that will be helpful in exploring their biomedical applications.

Dynamic control of the mode-locked fiber laser using a GO/PS modulator.

This Letter proposes a novel, to the best of our knowledge, transistor-like optical fiber modulator composed of graphene oxide (GO) and polystyrene (PS) microspheres. Unlike previously proposed schemes based on waveguides or cavity enhancement, the proposed method can directly enhance the photoelectric interaction with the PS microspheres to form a light local field. The designed modulator exhibits a distinct optical transmission change (62.8%), with a power consumption of <10 nW. Such low power consumption enables electrically controllable fiber lasers to be switched in various operational regimes, including continuous wave (CW), Q switched mode-locked (QML), and mode-locked (ML). With this all-fiber modulator, the pulse width of the mode-locked signal can be compressed to 12.9 ps, and the corresponding repetition rate is 21.4 MHz.

Narrow-linewidth single-polarization fiber laser using non-polarization optics.

Single longitudinal mode and single polarization are basic requirements of high performance fiber lasers, while their realizations are nontrivial, owing to the long laser cavity and lack of polarization selection of ordinary optical fibers. Here, we demonstrate an all-fiber narrow-linewidth laser realized on an external high-Q fiber ring, with combined functions of single-longitude-mode selection and linewidth reduction. A single-longitude-mode laser with a high polarization extinction ratio of ∼40dB and low white frequency noise at 0.3Hz2/Hz is achieved, corresponding to a fundamental linewidth of ∼0.92Hz. Using all non-polarization fiber components and ordinary gain fiber, our scheme shows the realization of narrow-linewidth single-polarization fiber lasers in a simple and cost-effective way, promising for broadband applications.

Narrow-linewidth self-injection locked diode laser with a high-Q fiber Fabry-Perot resonator.

Narrow-linewidth lasers are essential for various applications, but are limited by their size, weight, power, and cost requirements. Here we demonstrate a self-injection locked diode laser fabricated with a high quality factor fiber Fabry-Perot resonator, with a 145 Hz free-running linewidth. The locking scheme is all-fiber for plug-and-play operation. White frequency noise of 50Hz2/Hz is measured with over 42 dB reduction from the low-cost TO-can distributed feedback laser diode, and shows its wide applications in a compact and cost-effective way.

Effects of salts on the self-assembly behavior and antibacterial activity of a surfactant-like peptide.

Self-assembling peptides have become one of the most promising antibacterial agents due to their superior properties, such as simple molecular composition, favorable assembly structures, and rich designability. For maximum application in vivo, their activities in the presence of salts are desirable, however, the potent correlation between peptide nanostructures, antibacterial activity, and salt resistance behavior remains poorly explored. Previously, we have demonstrated that the potent antibacterial activity of a designed surfactant-like peptide Ac-A9K-NH2 benefited from its high self-assembly ability and appropriate size of its self-assembled nanostructures. In this study, we investigated the effect of salts on its self-assembly behavior and antibacterial activity. The results indicated that the flexible and long nanofibrils formed by Ac-A9K-NH2 in the presence of CaCl2 were adverse to its membrane insertion, leading to the reduction of antibacterial activity. Comparatively, Ac-A9K-NH2 maintained its potent antibacterial activity in the presence of NaCl due to its suitable shape and size of nanostructures. The newly formed nanofibers and nanorods facilitated the penetration of peptides into the bacterial membrane, forming nanopores and eventually leading to the lysis of bacteria. The high antibacterial activity and NaCl tolerance of Ac-A9K-NH2 make it a promising antibacterial agent at elevated salt concentrations.

[Prenatal exposure to lipopolysaccharide results in vascular renin-angiotensin system dysfunction in offspring rats].

OBJECTIVE: To explore the impact of prenatal exposure to lipopolysaccharide on renin-angiotensin system of offspring rats. METHODS: Six pregnant SD rats were randomly divided into 2 groups. The rats in the lipopolysaccharide (LPS) group were treated with LPS 0.79 mg/kg (i.p.) on the 8th, 10th and 12th day of gestation, and rats in the control group were treated with saline at the same time points. The blood pressure of offspring rats was measured by the tail cuff method. Protein expression of Angiotensin II (AngII) in thoracic aorta vessel was determined by immunohistochemistry. Protein expressions of AngII type 1 and type 2 receptor in thoracic aorta vessel were detected by Western blot. RESULTS: Blood pressure of 12-week-old offspring rats of LPS group was significantly higher than that of 12-week-old offspring rats of control group (P < 0.01). The protein expression of AngII and AngII type 1 receptor in thoracic aorta vessel were significantly higher while protein expression of AngII type 2 receptor was lower in 15-week-old offspring rats of LPS group than in control group, resulting in a significant increase in the ratio of AngII type 1 receptor/AngII type 2 receptor in the aorta at 15-week-old of offspring rats than in 15-week-old offspring rats of control group (P < 0.01). CONCLUSION: Prenatal lipopolysaccharide exposure results vascular renin-angiotensin system dysfunction, which may play an important role on the pathogenesis of hypertension development in offspring rats.

Prenatal exposure to inflammation induced by zymosan results in activation of intrarenal renin-angiotensin system in adult offspring rats.

Prenatal exposure to inflammation produces offspring that are hypertensive in adulthood. The present study was to explore the role of intrarenal renin-angiotensin (Ang) system in the development of hypertension programmed by prenatal exposure to zymosan. Pregnant rats were randomly divided into control group and zymosan group (n = 6). Rats in these two groups were administered intraperitoneally with 0.5 ml vehicle and 2.37 mg/kg zymosan, respectively, on the eighth, tenth, and 12th day during gestation. The results showed the glomerular number and creatinine clearance rate decreased significantly in offspring of zymosan-treated rats. The renal cortex renin mRNA expression, Ang II-positive cells in renal cortex, and Ang II expression in renal medulla increased significantly in offspring of zymosan-treated rats at 7, 16, and 25 weeks of age. The plasma renin activity and Ang II concentration were unchanged. In conclusion, prenatal exposure to zymosan resulted in the activation of intrarenal renin-Ang system in adult offspring rats.

Prenatal exposure to lipopolysaccharide alters the intrarenal renin-angiotensin system and renal damage in offspring rats.

Prenatal exposure to inflammation produces offspring that are hypertensive in adulthood. This study explored alterations of the renin-angiotensin system (RAS) during the development of hypertension induced by prenatal exposure to lipopolysaccharide (LPS). In addition, the effects of an inhibitor of the nuclear transcription factor (NF)-kappaB (pyrrolidine dithiocarbamate, PDTC) on this process were assessed. Pregnant rats were randomly divided into four groups (n=8): a control group, an LPS group, a PDTC group and an LPS+PDTC group. The rats in these groups were intraperitoneally administered vehicle, 0.79 mg kg(-1) LPS, 100 mg kg(-1) PDTC or LPS plus PDTC, respectively. LPS was given on the 8th, 10th and 12th days, whereas PDTC was given from the 8th to the 14th day during gestation. At various ages from day 1 to 25 weeks, plasma renin activity, plasma angiotensin II (Ang II) levels, renal function, glomerular number, mRNA expression levels of renal cortex renin and angiotensin-converting enzyme (ACE), the number of Ang II-positive cells and NF-kappaB activation were determined. The results showed that prenatal exposure to LPS resulted in significantly lower glomerular numbers and creatinine clearance rates and higher urinary protein and renal cortex ACE mRNA expression in adult offspring. Prenatal LPS also decreased the renal cortex renin mRNA expression and the number of Ang II-positive cells in offspring at 1 day of age, but these increased at 7, 16 and 25 weeks, whereas the plasma renin activity and Ang II concentration remained unchanged. Simultaneously, PDTC treatment markedly reversed the action of LPS. In conclusion, prenatal exposure to LPS resulted in alteration of the intrarenal RAS and renal damage in adult offspring rats.