Disinfection of Escherichia Coli Gram Negative Bacteria Using Surface Modified TiO2: Optimization of Ag Metallization and Depiction of Charge Transfer Mechanism

The antibacterial activity of silver deposited TiO₂ (Ag‐TiO₂) against Gram negative Escherichia coli bacteria was investigated by varying the Ag metal content from 0.10 to 0.50% on the surface of TiO₂. Ag depositions by the photoreduction method were found to be stable. Surface silver metallization was confirmed by EDAX and XPS studies. Photoluminescence studies show that the charge carrier recombination is less for 0.1% Ag‐TiO₂ and this catalyst shows superior bactericidal activity under solar light irradiation compared to Sol gel TiO₂ (SG‐TiO₂) due to the surface plasmon effect. The energy levels of deposited Ag are dependent on the Ag content and it varies from ?4.64 eV to ?1.30 eV with respect to the vacuum energy level based on atomic silver to bulk silver deposits. The ability of electron transfer from Ag deposit to O₂ depends on the position of the energy levels. The 0.25% and 0.50% Ag depositions showed detrimental effect on bactericidal activity due to the mismatch of energy levels. The effect of the EROS (External generation of the Reactive Oxygen Species by 0.1% Ag‐TiO₂) and IROS (Interior generation of Reactive Oxygen Species within the bacteria) on the bactericidal inactivation is discussed in detail.     

Synthesis and Biological Evaluation of Novel Bis[1,2,4]triazolo[3,4‐b] [1,3,4]oxadiazoles

A series of novel 6‐2‐methoxy‐5‐[4‐methoxy‐3‐(3‐aryl[1,2,4]triazolo[3,4‐b][1,3,4]oxadiazol‐6‐yl)benzyl]phenyl‐3‐aryl[1,2,4]triazolo[3,4‐b][1,3,4]oxadiazoles 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j has been synthesized and characterized via IR, ¹H NMR, ¹³C NMR, MS, and elemental analyses. Compounds 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j were also screened for their antibacterial activity against Gram‐positive bacteria viz. Bacillus subtilis (MTCC 441), Bacillus sphaericus (MTCC 11), and Staphylococcus aureus (MTCC 96), and Gram‐negative bacteria viz. Pseudomonas aeruginosa (MTCC 741), Klobsinella aerogenes (MTCC 39), and Chromobacterium violaceum (MTCC 2656). The antibacterial screening reveal that the presence of 2,4‐difluorophenyl ( 7e ) or 4‐nitrophenyl ( 7f ) of 2‐pyrazyl ( 7i ), or 2‐furyl ( 7j ) on the triazole moiety exhibited potent inhibitory activity comparable with the standard drug streptomycin, at the tested concentrations, and emerged as potential molecules for further development.     

Visible Light Photocatalyst Anatase Phased TiO2 Nanoparticles for Enhanced Antibacterial Performance

This study reports the development of anatase TiO₂ synthesized by facile photon-induced method (PIM) at various reaction times of 6 days, 8 days, 10-day samples. The 10 days TiO₂ sample shows stable anatase phase, whereas 100% rutile phase at the same temperature was observed for standard TiO₂. Mainly, the PIM was used to tuning the properties of visible light absorbance TiO₂ photocatalyst used for improving antibacterial performance. The antibacterial activity of TiO₂ against Staphylococcus aureus and Escherichia coli was determined by the agar disc diffusion method. Anatase TiO₂ nanoparticles demonstrated excellent antibacterial activity against extracellular S. aureus with 80% and E. coli with 82% killing efficacy at concentrations as low as 100 μg/mL, which is 100% faster than the standard and other pure TiO₂ reported earlier. The obtained undoped anatase Titania with enhanced chemical reactivity has great potential for antibacterial properties. Moreover, the smaller crystallite size (25 nm) and narrowing bandgap (2.96 eV) TiO₂ nanoparticles were more effective in killing bacteria compared with standard TiO₂. Therefore, this work indicated that anatase phased TiO₂ under visible light absorbance has good potential with excellent clinical applications.

     

Defect Analysis and Defect Tolerant Design of Multi-port SRAMs

Multi-port SRAMs are often implemented using static random access memory (SRAM) due to its fast operation and the ability to support multiple read and write operations simultaneously, thus increasing data throughput in embedded systems and meeting the expected demands of parallel or pipelined microprocessors. With the continuous scaling of transistor feature size, designing low power robust memories and investigating their failure characteristics become critical. In this paper, we study the defects occurring in the multi-port SRAM cells. The memory is modeled at the transistor level and analyzed for electrical defects by applying a set of test patterns. Not only have existing models been taken into account in our simulation but also a new fault model, namely, simultaneous deceptive destructive read fault for the multi-port memory is introduced. In addition, we extend our study to the defect tolerant design of memories by proposing a differential current-mode sense amplifier for 3-port SRAM based register file. We examine the fault models of resistive defects within the SRAM cell and its failure boundary. A read disturb fault for multi-port memories is tested on the faulty cell by simultaneous read operations with different numbers of ports. Experimental results show that the proposed current-mode sensing scheme has improvements for memory fault-tolerance of resistive defects at 4.6× for dual-port read and 5.8× for 3-port read compared to voltage-mode sensing with 0.18 μm manufacturing process technology.     

Large-swing CMOS buffer amplifier

A circuit configuration for a CMOS buffer amplifier is described. The circuit, which is an enhancement of a previously reported buffer amplifier, features a large output voltage swing and a well-controlled quiescent current. A buffer amplifier of this type has been implemented in a 1.5-μm CMOS technology. The prototype occupies an area of 275 mil². It works with a 5-V supply and can drive more than 4.2 V (peak to peak) in to 300 Ω with a total harmonic distortion of less than 0.025%     

Multistage monostable multivibrator using load-coupled regenerative feedback

A monostable multivibrator configuration using a new technique of regenerative feedback is discussed. This circuit provides an elegant alternative in situations wherein several monostable multivibrators have to be connected in tandem.     

Synthesis and biological evaluation of novel methylene‐bis‐[1,5]‐benzodiazepines

A series of novel methylene‐bis‐chalcones 3 was prepared by the reaction of 5‐(3‐formyl‐4‐hydroxybenzyl)‐2‐hydroxy benzaldehyde 2 with different acetophenones, subsequent treatment of compound 3 with an appropriate o‐phenylenediamine gave the corresponding methylene‐bis‐[1,5]‐benzodiazepines 4/5 in good yields. Characterization of the new compounds has been done by means of IR, ¹H NMR, MS and elemental analyses. The antibacterial and antifungal activity of the compounds has also been evaluated.     

Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8′‐methylene‐bis‐4‐oxo‐1H and 2H‐chromeno[4,3‐C]pyrazoles

The ethyl ester of 5,5′‐methylene‐bis‐salicyclic acid 3 was prepared by the esterification of 5,5′‐methylene‐bis‐salicylic acid 2 . The compound 3 on reacting with ethylacetoacetate yields 6,6′‐methylenebis‐(3‐acetyl‐4‐hydroxycoumarin) 4 . The compound 4 was regioselectively converted into either 8,8′‐methylene‐bis‐(4‐oxo‐1H‐chromeno[4,3‐c]pyrazoles) 6 or 8,8′‐methylene‐bis(‐4‐oxo‐2H‐chromeno[4,3‐c]‐pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions.     

UVA Light‐mediated Ascorbate Oxidation in Human Lenses

Whether ascorbate oxidation is promoted by UVA light in human lenses and whether this process is influenced by age and GSH levels are not known. In this study, we used paired lenses from human donors. One lens of each pair was exposed to UVA light, whereas the other lens was kept in the dark for the same period of time as the control. Using LC‐MS/MS analyses, we found that older lenses (41–73 years) were more susceptible to UVA‐induced ascorbate oxidation than younger lenses (18–40 years). Approximately 36% of the ascorbate (relative to control) was oxidized in older lenses compared to ~16% in younger lenses. Furthermore, lenses with higher levels of GSH were less susceptible to UVA‐induced ascorbate oxidation compared to those with lower levels, and this effect was not dependent on age. The oxidation of ascorbate led to elevated levels of reactive α‐dicarbonyl compounds. In summary, our study showed that UVA light exposure leads to ascorbate oxidation in human lenses and that such oxidation is more pronounced in aged lenses and is inversely related to GSH levels. Our findings suggest that UVA light exposure could lead to protein aggregation through ascorbate oxidation in human lenses.     

Kinetics and Thermodynamics of Glycans and Glycoproteins Binding to Holothuria scabra Lectin: A Fluorescence and Surface Plasmon Resonance Spectroscopic Study

Holothuria scabra produces a monomeric lectin (HSL) of 182 kDa. HSL showed strong antibacterial activity and induced bacterial agglutination under in vitro conditions, indicating its role in animals’ innate immune responses. Very few lectins have been reported from echinoderms and none of these lectins have been explored in detail for their sugar-binding kinetics. Affinity, kinetics and thermodynamic analysis of glycans and glycoproteins binding to HSL were studied by fluorescence and surface plasmon resonance spectroscopy. Lectin binds with higher affinity to O-linked than N-linked asialo glycans, and the affinities were relatively higher than that for sialated glycans and glycoproteins. T-antigen α-methyl glycoside was the most potent ligand having the highest affinity (Ka 8.32 ×10⁷ M^?1). Thermodynamic and kinetic analysis indicated that the binding of galactosyl Tn-antigen and asialo glycans is accompanied by an enthalpic contribution in addition to higher association rate coupled by low activation energy for the association process. Presence of sialic acid or protein matrix inhibits binding. Higher affinity of HSL for O-glycans than N-glycans had biological implications; since HSL specifically recognizes bacteria, which have mucin or O-glycan cognate on their cell surfaces and play a major role in animal innate immunity. Since, HSL had higher affinity to T-antigen, makes it a useful tool for cancer diagnostic purpose.