The design of cell-selective tryptophan and arginine-rich antimicrobial peptides by introducing hydrophilic uncharged residues.

Antimicrobial peptides (AMPs) are considered to be powerful weapons in the fight against traditional antibiotic resistance due to their unique membrane-disruptive mechanism. The combination of traditional and classical hydrophobic tryptophan (W) residues and hydrophilic charged arginine (R) residues is considered as the first choice for the minimalist design of AMPs due to its potent performance in antibacterial activity. However, some W- and R-rich AMPs that are not rationally designed and contain excessive repeats of W and R residues may cause severe cytotoxicity and hemolysis. To address this issue, we designed the (WRX)n (where X = hydrophilic uncharged amino residues; n = number of repeat units) series engineered peptides with high cell selectivity by introducing hydrophilic uncharged threonine (T), serine (S), glutamine (Q) or asparagine (N) residues into the minimalist design of W- and R-rich AMPs. The results showed that the introduction of these hydrophilic uncharged amino residues, especially T residues, significantly improved the cell selectivity of the W- and R-rich engineered peptides. Among (WRX)n series engineered peptides, T6 presents a mixture structure of ß-turn and α-helix. It has broad spectrum and potent antibacterial activity (no activity against probiotics), good biocompatibility, high selectivity index, strong tolerance (physiological salts, serum acid, alkali, and heat conditions), rapid and efficient time-kill kinetics, and no tendency of resistance. Studies on antibacterial mechanism show that T6 exert antibacterial activity mainly by disrupting bacterial cell membrane and inducing the accumulation of reactive oxygen species in bacterial cells. Furthermore, T6 exhibited potent antibacterial and antiinflammatory capabilities in vivo in a mouse peritonitis-sepsis model infected with Escherichia coli. In conclusion, our study confirms an effective strategy for the minimalist design of highly cell selective W- and R-rich AMPs by introducing hydrophilic uncharged T residues, which may trigger widespread attention to hydrophilic uncharged amino acid residues, including T residues, and provide new insights into the design of peptide-based antibacterial biomaterials. STATEMENT OF SIGNIFICANCE: We have introduced hydrophilic uncharged T, S, Q or N residues into the minimalist design of W- and R-rich engineered peptides and found that the introduction of these hydrophilic uncharged amino residues, especially the T residues, can significantly improve the cell selectivity of W- and R-rich engineered peptides. The target compound T6 showed potent antibacterial activity, high cell selectivity, strong tolerance, good in vivo efficacy and killed bacteria through multiple mechanisms mainly membrane-disruptive. These findings may spark widespread interest in hydrophilic uncharged amino acid residues, and provide new insights into the design of peptide-based antimicrobial biomaterials.

Arsenic in drinking water: overview of removal strategies and role of chitosan biosorbent for its remediation.

Accessibility to clean drinking water often remains a crucial task at times. Among other water pollutants, arsenic is considered a more lethal contaminant and has become a serious threat to human life globally. This review discussed the sources, chemistry, distribution, and toxicity of arsenic and various conventional technologies that are in option for its removal from the water system. Nowadays, biosorbents are considered the best option for arsenic-contaminated water treatment. We have mainly focused on the need and potential of biosorbents especially the role of chitosan-based composites for arsenic removal. The chitosan-based sorbents are economically more efficient in terms of their, low toxicity, cost-effectiveness, biodegradability, eco-friendly nature, and reusability. The role of various modification techniques, such as physical and chemical, has also been evaluated to improve the physicochemical properties of biosorbent. The importance of adsorption kinetic and isotherm models and the role of solution pH and pHPZC for arsenic uptake from the polluted water have also been investigated. Some other potential applications of chitosan-based biosorbents have also been discussed along with its sustainability aspect. Finally, some suggestions have been highlighted for further improvements in this field.

Ammonia inhalation-induced inflammation and structural impairment in the bursa of fabricius and thymus of broilers through NF-κB signaling pathway.

Ammonia (NH3) is a toxic, environmental pollutant, and irritant gas. Previous studies reported the toxic effects of NH3 which led to inflammation in various organs of chicken. However, the exact mechanism of NH3-induced inflammation in chicken lymphoid organs bursa of fabricius (BF) and thymus is still elusive. Thus, this study was designed to investigate NH3-induced inflammation in chicken BF and thymus. Experimental chickens were divided into low (5.0 mg/m3), middle (10.0-15.0 mg/m3), and high (20.0-45.0 mg/m3) NH3-treated groups. To investigate NH3-induced inflammation in chicken's BF and thymus, histological observation, NO content and iNOS activity, inflammatory cytokine contents, and mRNA levels were performed by light microscopy, microplate spectrophotometer, ELISA assay, and qRT-PCR. The finding of the present study showed that NH3 exposure reduced BF and thymus index, increased nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity, inflammatory cytokine contents and mRNA levels of nuclear factor-kappa B (NF-κB), cyclooxygenase-2 (Cox-2), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), IL-10, IL-1ß, IL-18, toll-like receptor 2A (TLR-2A), and iNOS. Histopathological examination revealed signs of inflammation including increased nuclear debris and vacuoles in the cortex and medulla of thymus and bursal follicles. Conclusively, our findings displayed that NH3 exposure affects the normal function of BF and thymus and led inflammation. The data provided a new ground for NH3-induced toxicity and risk assessment in chicken production.

Missing Link Prediction using Common Neighbor and Centrality based Parameterized Algorithm.

Real world complex networks are indirect representation of complex systems. They grow over time. These networks are fragmented and raucous in practice. An important concern about complex network is link prediction. Link prediction aims to determine the possibility of probable edges. The link prediction demand is often spotted in social networks for recommending new friends, and, in recommender systems for recommending new items (movies, gadgets etc) based on earlier shopping history. In this work, we propose a new link prediction algorithm namely "Common Neighbor and Centrality based Parameterized Algorithm" (CCPA) to suggest the formation of new links in complex networks. Using AUC (Area Under the receiver operating characteristic Curve) as evaluation criterion, we perform an extensive experimental evaluation of our proposed algorithm on eight real world data sets, and against eight benchmark algorithms. The results validate the improved performance of our proposed algorithm.

Multiple Strategy Optimization of Specifically Targeted Antimicrobial Peptide Based on Structure-Activity Relationships to Enhance Bactericidal Efficiency.

Unlike traditional broad-spectrum antibacterial agents, specifically targeted antimicrobial peptides (STAMPs) are difficult for bacteria to develop resistance to due to their unique membrane lytic mechanism. Additionally, STAMPs can maintain a normal ecological balance and provide long-term protection to the body. However, therapeutic applications of STAMPS are hindered by their weak activity and imperfect specificity, as well as lack of knowledge in understanding their structure-activity relationships. To investigate the effects of different parameters on the biological activities of STAMPs, a peptide sequence, WKKIWKDPGIKKWIK, was truncated, extended, and provided with an increased charge and altered amphipathicity. In addition, a novel template modification method for attaching a phage-displayed peptide, which recognized and bound to Escherichia coli (E. coli) cells, to the end of the sequence was introduced. Compared with the traditional template modification method, peptide 13, which contained a phage-displayed peptide at the C-terminus, exhibited superior narrow-spectrum antibacterial activity against E. coli compared to that of parental peptide 2, and the activity and specificity of peptide 13 were increased by 5.0 and 2.4 times, respectively. Additionally, peptide 13 showed low cytotoxicity and relatively desirable salt, serum, acid, alkaline and heat stability. In this study, peptide 13 specifically killed E. coli by causing cytoplasmic membrane rupture and cytosol leakage. In summary, these findings are useful for improving the activity and specificity of STAMPs and show that peptide 13 is able to combat the growing threat of E. coli infections.

Nanoniosome-encapsulated levoflaxicin as an antibacterial agent against Brucella.

A study was conducted to examine the prevalence of brucellosis (in animal farms) in the vicinity of Islamabad and Rawalpindi. A total of 170 milk samples were collected randomly from several farmhouses. The collected milk samples were initially screened by a Brucella selective medium. The bacterial isolates grown on the selective medium were subjected to biochemical identification for further confirmation of Brucella species. Among the tested samples, 28 (16.4%) were found positive for selective medium and 14 (8.2%) were found positive after biochemical confirmation. The antimicrobial susceptibility of several antibiotics performed by the disc-diffusion method did not yield any significant findings. Encapsulating antimicrobial drugs in unilamellar niosomes is an effective approach to treat the endemic infection. In this study, the antimicrobial activity of niosome-encapsulated levofloxacin is compared with free drug. The drug-encapsulating and empty niosomes were synthesized by using two surfactants Tween 80 and Span 40. Niosomal characterization included electron microscopy, dynamic light scattering, and zeta potential. The encapsulation efficiency was found to be 78% and 74% for Span 40 and Tween 80 niosomes, respectively. The antibacterial activity of niosomal levofloxacin was evaluated against the identified Brucella species and the antimicrobial activity of the free drug was increased many folds after encapsulation. In this study, levofloxacin niosomes were successfully synthesized against Brucellosis.

Effect of terminal arrangement of tryptophan on biological activity of symmetric α-helix-forming peptides.

It is traditionally believed that the distribution of tryptophan (Trp) residues is critical for the novo design of antimicrobial peptides (AMPs). However, there is scarce knowledge regarding Trp residues arrangement at the head group level. Thus, a set of α-helical AMPs containing different Trp residue arrangements at the N-/C-terminal of sequence were designed to increase the strategy database and analyze their biological activities. The arrangement of the N-terminal Trp residue significantly improved the bacteriostatic activity of the peptides, but the C-terminal Trp residue arrangement reduced the biocompatibility of them. WL and LW were effective against Gram-negative microbes and had high selectivity for bacteria as compared to human erythrocytes and mammalian cells. They both maintained a relatively desirable activity in the presence of physiological salts and serum. It is observed through electron microscope, flow cytometry and fluorescence spectroscopy that target peptides can penetrate bacterial cell membrane and kill it by damaging cell membrane integrity. Collectively, we determined the structure-activity relationship of Trp residue distributions in a symmetric sequence structure and filled the gap in knowledge related to Trp arrangements at the head group level. The obtained results will be helpful in designing of artificial peptide-based antimicrobials.

Short, symmetric-helical peptides have narrow-spectrum activity with low resistance potential and high selectivity.

Broad-spectrum antibiotics have, until now, been the mainstay of antibiotic therapy. However, the increasing threat of drug-resistant bacteria and the ecological imbalance of normal microbial communities have forced a reconsideration of the best strategies to treat such pathogens. Therefore, antibacterial agents with specific abilities of eliminating pathogens may provide long-term protection. Antimicrobial peptides (AMPs), which can be optimized by modifying their primary sequences, are regarded as potentially valuable in development of pathogen-specific agents. To obtain efficient narrow-spectrum AMPs, database-filtering technology, which filters the most probable amino acid composition, positive charge, sequence length and hydrophobic content of peptides against Gram-negative bacteria, was taken as the first step. Then, the filtered parameters were distributed and modified into an α-helical symmetrical structure by considering the structure-function relationship of synthesized antimicrobial peptides. Finally, short, safe and stable peptides against Escherichia coli, Salmonella pullorum and Pseudomonas aeruginosa were successfully identified. The potential peptides F1 and F4 showed low cell toxicity, low resistance potential and low salt sensitivity. CD spectroscopy of the peptides illustrated that F1 and F4 exhibited a tendency towards an α-helical structure in a membrane-mimetic environment. Indeed, fluorescence spectroscopy and electron microscopy analyses indicated that the shorter potential sequence F4 killed the bacteria by causing physical destruction of the bacterial membrane and cytosol leakage. In the mouse model test, F4 reduced the bacterial load in major organs and the cytokine (TNF-α, IL-6, and IL-1ß) levels in serum significantly (P < 0.05). Collectively, this symmetric-helical distribution, dependent on database-filtering parameters, is a promising strategy for designing effective smart AMPs with high cell selectivity, and it also provides new insights into the design and optimization of pathogen-specific biomaterials.

Clinico-radiographic study of odontogenic cysts at a tertiary care centre.

BACKGROUND: Cysts of the jaws constitute an important pathology in the oral and maxillofacial region and are broadly classified as odontogenic and non-odontogenic. Objective of this study was to document the clinical and radiographic presentation of odontogenic cysts at a tertiary care centre. METHODS: In this descriptive case-series, patients presenting with features of suspected cystic lesions of the jaws were investigated using radiographs and incisional biopsy. Subjects showing clinico- radiographic features of odontogenic cyst(s) with subsequent confirmation on histopathological examination were included. RESULTS: A total of 112 subjects were investigated for suspected jaw cysts and cystic diagnosis of odontogenic cysts was confirmed in 100 patients with 53 males (53%) and 47 females (47%). The age range of patients was from 12-55 years. Radicular cyst was the most commonly diagnosed odontogenic cyst (63%) followed by dentigerous cyst (22%) and odontogenickeratocyst (14%). Anterior maxilla was the most affected site (44%) followed by posterior mandible (30%). CONCLUSION: Odontogenic cysts constitute an established pathology affecting the jaws with varying frequency. This study augments the data cited from Western countries and re-emphasizes the need for early diagnosis and prompt management. It also highlights the differences in the presentation of odontogenic cysts as observed in the current series.

Use of silastic as interpositional material in the management of unilateral temporomandibular joint ankylosis.

BACKGROUND: Ankylosis is a very common condition developed mainly after damage to mandibular condyles or temporomandibular joint (TMJ) at a growing age. Different autogenous and alloplastic interpositional materials have been attempted after the resection of the ankylotic bone to achieve desirable results. This condition is relatively common in Pakistan. We treated TMJ ankylosis with alloplastic medical grade silicone "silastic" interpositional arthroplasty. Eight joints accompanied ipsilateral or contralateral coronoidectomy to achieve desirable results. METHOD: All patients were presented at Punjab Dental Hospital Lahore. Sixty-one joints with unilateral TMJ ankylosis were underwent surgery after careful examination and final radiographic confirmation. The preoperative CT scan was also performed in few patients. RESULTS: The postoperative measurements of the interincisal opening with lateral and protrusive jaw movements were criteria for success of surgery. The lateral and protrusive jaw movements were assessed as excellent, good and poor. Less than 25 mm interincisal opening was considered as poor jaw opening. CONCLUSION: The overall success rate was 98.4 % with 84 % desirable interincisal jaw opening. Less than 5% patients were observed with poor jaw opening. The immediate late complications were transient and were included oedema, weakness of a branch of the facial nerve on the operated side. Two implants were infected along with one wire in the first month of surgery and were removed under local anaesthesia without further complication.