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A new semi-empirical kinetic method for the determination of ion exchange constants for the counterions of cationic micelles

Khan MN

Adv Colloid Interface Sci, 2010 Sep 15;159(2):160-79.
PMID: 20673861 DOI: 10.1016/j.cis.2010.06.005

A new method, based upon semi-empirical kinetic approach, for the determination of ion exchange constant for ion exchange processes occurring between counterions at the cationic micellar surface is described in this review article. Basically, the method involves a reaction kinetic probe which gives observed pseudo-first-order rate constants (k(obs)) for a nucleophilic substitution reaction between the nonionic and anionic reactants (R and S) in the presence of a constant concentration of both reactants as well as cationic micelles and varying concentrations of an inert inorganic or organic salt (MX). The observed data (k(obs), versus [MX]) fit satisfactorily (in terms of residual errors) to an empirical equation which could be derived from an equation explaining the mechanism of the reaction of the kinetic probe in terms of pseudophase micellar (PM) model coupled with another empirical equation. This (another) empirical equation explains the effect of [MX] on cationic micellar binding constant (K(S)) of the anionic reactant (say S) and gives an empirical constant, K(X/S). The magnitude of K(X/S) is the measure of the ability of X(-) to expel S(-) from a cationic micellar pseudophase to the bulk aqueous phase through ion exchange X(-)/S(-). The values of K(X/S) and K(Y/S) (where Y(-) is another inert counterion) give the ion exchange constant, K(X)(Y) (=K(X)/K(Y) where K(X) and K(Y) represent cationic micellar binding constants of X(-) and Y(-), respectively). The suitability of this method is demonstrated by the use of three different reaction kinetic probes and various MX.
Aconitum lycoctonum L. (Ranunculaceae) mediated biogenic synthesis of silver nanoparticles as potential antioxidant, anti-inflammatory, antimicrobial and antidiabetic agents

Khan ZUR, Assad N, Naeem-Ul-Hassan M, Sher M, Alatawi FS, Alatawi MS, et al.

BMC Chem, 2023 Sep 28;17(1):128.
PMID: 37770921 DOI: 10.1186/s13065-023-01047-5

In this study, a polar extract of Aconitum lycoctonum L. was used for the synthesis of silver nanoparticles (AgNPs), followed by their characterization using different techniques and evaluation of their potential as antioxidants, amylase inhibitors, anti-inflammatory and antibacterial agents. The formation of AgNPs was detected by a color change, from transparent to dark brown, within 15 min and a surface resonance peak at 460 nm in the UV-visible spectrum. The FTIR spectra confirmed the involvement of various biomolecules in the synthesis of AgNPs. The average diameter of these spherical AgNPs was 67 nm, as shown by the scanning electron micrograph. The inhibition zones showed that the synthesized nanoparticles inhibited the growth of Gram-positive and negative bacteria. FRAP and DPPH assays were used to demonstrate the antioxidant potential of AgNPs. The highest value of FRAP (50.47% AAE/mL) was detected at a concentration of 90 ppm and a DPPH scavenging activity of 69.63% GAE was detected at a concentration of 20 µg/mL of the synthesized AgNPs. 500 µg/mL of the synthesized AgNPs were quite efficient in causing 91.78% denaturation of ovalbumin. The AgNPs mediated by A. lycoctonum also showed an inhibitory effect on α-amylase. Therefore, AgNPs synthesized from A. lycoctonum may serve as potential candidates for antibacterial, antioxidant, anti-inflammatory, and antidiabetic agents.
Bisindolylmethane thiosemicarbazides as potential inhibitors of urease: Synthesis and molecular modeling studies

Taha M, Ullah H, Al Muqarrabun LMR, Khan MN, Rahim F, Ahmat N, et al.

Bioorg Med Chem, 2018 01 01;26(1):152-160.
PMID: 29183662 DOI: 10.1016/j.bmc.2017.11.028

Bisindolylmethane thiosemicarbazides 1-18 were synthesized, characterized by 1H NMR and ESI MS and evaluated for urease inhibitory potential. All analogs showed outstanding urease inhibitory potentials with IC50 values ranging between 0.14 ± 0.01 to 18.50 ± 0.90 μM when compared with the standard inhibitor thiourea having IC50 value 21.25 ± 0.90 μM. Among the series, analog 9 (0.14 ± 0.01 μM) with di-chloro substitution on phenyl ring was identified as the most potent inhibitor of urease. The structure activity relationship has been also established on the basis of binding interactions of the active analogs. These binding interactions were identified by molecular docking studies.
Fulltext Cancer Incidence, Mortality, Years of Life Lost, Years Lived With Disability, and Disability-Adjusted Life Years for 29 Cancer Groups From 2010 to 2019: A Systematic Analysis for the Global Burden of Disease Study 2019

Global Burden of Disease 2019 Cancer Collaboration, Kocarnik JM, Compton K, Dean FE, Fu W, Gaw BL, et al.

JAMA Oncol, 2022 Mar 01;8(3):420-444.
PMID: 34967848 DOI: 10.1001/jamaoncol.2021.6987

IMPORTANCE: The Global Burden of Diseases, Injuries, and Risk Factors Study 2019 (GBD 2019) provided systematic estimates of incidence, morbidity, and mortality to inform local and international efforts toward reducing cancer burden.
OBJECTIVE: To estimate cancer burden and trends globally for 204 countries and territories and by Sociodemographic Index (SDI) quintiles from 2010 to 2019.
EVIDENCE REVIEW: The GBD 2019 estimation methods were used to describe cancer incidence, mortality, years lived with disability, years of life lost, and disability-adjusted life years (DALYs) in 2019 and over the past decade. Estimates are also provided by quintiles of the SDI, a composite measure of educational attainment, income per capita, and total fertility rate for those younger than 25 years. Estimates include 95% uncertainty intervals (UIs).
FINDINGS: In 2019, there were an estimated 23.6 million (95% UI, 22.2-24.9 million) new cancer cases (17.2 million when excluding nonmelanoma skin cancer) and 10.0 million (95% UI, 9.36-10.6 million) cancer deaths globally, with an estimated 250 million (235-264 million) DALYs due to cancer. Since 2010, these represented a 26.3% (95% UI, 20.3%-32.3%) increase in new cases, a 20.9% (95% UI, 14.2%-27.6%) increase in deaths, and a 16.0% (95% UI, 9.3%-22.8%) increase in DALYs. Among 22 groups of diseases and injuries in the GBD 2019 study, cancer was second only to cardiovascular diseases for the number of deaths, years of life lost, and DALYs globally in 2019. Cancer burden differed across SDI quintiles. The proportion of years lived with disability that contributed to DALYs increased with SDI, ranging from 1.4% (1.1%-1.8%) in the low SDI quintile to 5.7% (4.2%-7.1%) in the high SDI quintile. While the high SDI quintile had the highest number of new cases in 2019, the middle SDI quintile had the highest number of cancer deaths and DALYs. From 2010 to 2019, the largest percentage increase in the numbers of cases and deaths occurred in the low and low-middle SDI quintiles.
CONCLUSIONS AND RELEVANCE: The results of this systematic analysis suggest that the global burden of cancer is substantial and growing, with burden differing by SDI. These results provide comprehensive and comparable estimates that can potentially inform efforts toward equitable cancer control around the world.
Fulltext Community's misconception about COVID-19 and its associated factors in Satkhira, Bangladesh: A cross-sectional study

Bakebillah M, Billah MA, Wubishet BL, Khan MN

PLoS One, 2021;16(9):e0257410.
PMID: 34506614 DOI: 10.1371/journal.pone.0257410

INTRODUCTION: Misconception related to coronavirus disease-2019 (COVID-19) have been spread out broadly and the the World Health Organization declared these as a major challenge to fight against the pandemic. This study aimed to assess COVID-19 related misconception among rural people in Bangladesh and associated socio-demographic and media related factors.
METHODS: Multistage sampling method was used to collect data (n = 210) from three unions of Satkhira District, Bangladesh. The dependent variable was the presence of COVID-19 related misconception (Yes, No) which was generated based on respondents' responses to a set of six questions on various types of misconception. Exposure variables were respondents' socio-demographic characteristics, mass media and social media exposure. Descriptive statistics were used to describe the characteristics of the respondents. Bivariate and multivariate logistic regression models were used to determine the factors associated with COVID-19 misconception.
RESULTS: More than half of the study respondents had one or more COVID-19 related misconception. Over 50% of the total respondents considered this disease as a punishment from God. Besides, many of the respondents reported that they do not think the virus causing COVID-19 is dangerous (59%) and it is a disease (19%). Around 7% reported they believe the virus is the part of a virus war (7.2%). The bivariate analysis found the presence of socio-demographic factors of the respondents, as well as the factors related to social and mass media, were significantly associated with the COVID-19's misconception. However, once all factors considered together in the multivariate model, misconception were found to be lower among secondary (AOR, 0.33, 95% CI: 0.13-0.84) and tertiary (AOR, 0.29, 95% CI: 0.09-0.92) educated respondents compared to the respondents with primary education.
CONCLUSION: This study obtained a very higher percentage of misconception about the COVID-19 among the respondents of Satkhira district in Bangladesh. This could be a potential challenge to fight against this pandemic which is now ongoing. Prioritizing mass and social media to disseminate evidence-based information as well as educate people about this disease are necessary.
Correction to: Aconitum lycoctonum L. (Ranunculaceae) mediated biogenic synthesis of silver nanoparticles as potential antioxidant, anti-infammatory, antimicrobial and antidiabetic agents

Khan ZUR, Assad N, Naeem-Ul-Hassan M, Sher M, Alatawi FS, Alatawi MS, et al.

BMC Chem, 2023 Oct 25;17(1):143.
PMID: 37880757 DOI: 10.1186/s13065-023-01058-2
Corrigendum to "Clinical use of mood stabilizers beyond treatment for bipolar disorder: The REAP-MS study" [Asian J. Psychiatry 85 (2023) 103613]

Chen CK, Yang SY, Park SC, Jang OJ, Zhu X, Xiang YT, et al.

Asian J Psychiatr, 2023 Nov;89:103650.
PMID: 37308390 DOI: 10.1016/j.ajp.2023.103650
Fulltext Design, synthesis, and spasmolytic activity of thiophene-based derivatives via Suzuki cross-coupling reaction of 5-bromothiophene-2-carboxylic acid: their structural and computational studies

Rasool N, Ikram HM, Rashid A, Afzal N, Hashmi MA, Khan MN, et al.

Turk J Chem, 2020;44(5):1410-1422.
PMID: 33488240 DOI: 10.3906/kim-1911-51

In the current research work, a facile synthesis of a series of novel thiophene-based derivatives of 5-bromothiophene-2-carboxylic acid ( 1 ) have been synthesized. All analogs ( 5a - 5e , 10a - 10f ) were obtained from the coupling reaction of 5-bromothiophene-2-carboxylic acid ( 1 ) and different arylboronic acids with moderate-to-good yields under controlled and optimal conditions. The structures of the newly synthesized compounds were characterized through spectral analysis and their spasmolytic activity, and most of the compounds exhibited potentially good spasmolytic effect. Among the synthesized analogs, compound phenethyl 5-(3,4-dichlorophenyl)thiophene-2-carboxylate ( 10d ) particular showed an excellent spasmolytic effect with an EC 50 value of 1.26. All of the compounds were also studied for their structural and electronic properties by density functional theory (DFT) calculations. Through detailed insight into frontier molecular orbitals of the compounds and their different reactivity descriptors, it was found that the compounds 10c and 5c are the most reactive, while 10a is the most stable in the series. Furthermore, compounds 10c and 5c showed a very good NLO response with the highest β values.
Determination of Relative Counterion Binding Constant to Cationic Micelles

Khalid K, Noh MAM, Zain SM, Khan MN

Top Curr Chem (Cham), 2017 Apr;375(2):45.
PMID: 28357712 DOI: 10.1007/s41061-017-0132-9

The efficiency of counterion affinity towards ionic micelles is often described in terms of the degree of counterion binding (β X ) to ionic micelles or the conventional ion-exchange constant ([Formula: see text]) or relative binding constant ([Formula: see text]) of X - and Br- counterions. This review describes the use of ionized phenyl salicylate ions, PSa-, as a new probe to determine [Formula: see text] values using a semiempirical spectrophotometric method. The value of [Formula: see text] is found to be comparable to reported values obtained using different probes by the semiempirical kinetic method as well as different physical methods. Application of semiempirical methods for calculation of [Formula: see text] or [Formula: see text] values involves an inherent assumption that these values are independent of the physicochemical characteristics of the probe molecule.
Determination of an ion exchange constant by the use of a kinetic probe: a new semiempirical kinetic approach involving the effects of 3-F- and 4-F-substituted benzoates on the rate of piperidinolysis of anionic phenyl salicylate in aqueous cationic micelles

Yusof NS, Khan MN

Langmuir, 2010 Jul 6;26(13):10627-35.
PMID: 20524703 DOI: 10.1021/la100863q

Pseudo-first-order rate constants (k(obs)) for the nucleophilic substitution reaction of piperidine (Pip) with ionized phenyl salicylate (PS(-)), obtained at a constant [Pip](T) (= 0.1 M), [PS(-)](T) (= 2 x 10(-4) M), [CTABr](T) (cetyltrimethylammonium bromide), < or = 0.06 M NaOH, and a varying concentration of MX (= 3-FC(6)H(4)CO(2)Na, 3-FBzNa and 4-FC(6)H(4)CO(2)Na, 4-FBzNa), follow the kinetic relationship k(obs) = (k(0) + thetaK(X/S)[MX])/(1 + K(X/S)[MX]) which is derived by the use of the pseudophase micellar (PM) model coupled with an empirical equation. The empirical equation explains the effects of [MX] on CTABr micellar binding constant (K(S)) of PS(-) that occur through X(-)/PS(-) ion exchange. Empirical constants theta and K(X/S) give the parameters F(X/S) and K(X/S), respectively. The magnitude of F(X/S) gives the measure of the fraction of micellized PS(-) transferred to the aqueous phase by the limiting concentration of X(-) through X(-)/PS(-) ion exchange. The values of F(X/S) and K(X/S) have been used to determine the usual thermodynamic ion exchange constant (K(X)(Y)) for ion exchange process X(-)/Y(-) on the CTABr micellar surface. The values of K(X)(Br) (where Br = Y) have been calculated for X = 3-FBzNa and 4-FBzNa. The mean values of K(X)(Br) are 12.8 +/- 0.9 and 13.4 +/- 0.6 for X(-) = 3-FBz(-) and 4-FBz(-), respectively. Nearly 3-fold-larger values of K(X)(Br) for X = 3-FBz(-) and 4-FBz(-) than those for X = Bz(-), 2-ClBz(-), 2-CH(3)Bz(-), and the 2,6-dichlorobenzoate ion (2,6-Cl(2)Bz(-)) are attributed to the presence of wormlike micelles in the presence of > 50 mM 3-FBz(-) and 4-FBz(-) in the [CTABr](T) range of 5-15 mM. Rheological properties such as shear thinning behavior of plots of shear viscosity versus the shear rate at a constant [3-FBz(-)] or [4-FBz(-)] as well as shear viscosity (at a constant shear rate) maxima as a function of the concentrations of 3-FBz(-) and 4-FBz(-) support the conclusion, derived from the values of K(X)(Br), for the probable presence of wormlike/viscoelastic micellar solutions under the conditions of the present study.
Fulltext Diseases, Injuries, and Risk Factors in Child and Adolescent Health, 1990 to 2017: Findings From the Global Burden of Diseases, Injuries, and Risk Factors 2017 Study

GBD 2017 Child and Adolescent Health Collaborators, Reiner RC, Olsen HE, Ikeda CT, Echko MM, Ballestreros KE, et al.

JAMA Pediatr, 2019 06 01;173(6):e190337.
PMID: 31034019 DOI: 10.1001/jamapediatrics.2019.0337

Importance: Understanding causes and correlates of health loss among children and adolescents can identify areas of success, stagnation, and emerging threats and thereby facilitate effective improvement strategies.
Objective: To estimate mortality and morbidity in children and adolescents from 1990 to 2017 by age and sex in 195 countries and territories.
Design, Setting, and Participants: This study examined levels, trends, and spatiotemporal patterns of cause-specific mortality and nonfatal health outcomes using standardized approaches to data processing and statistical analysis. It also describes epidemiologic transitions by evaluating historical associations between disease indicators and the Socio-Demographic Index (SDI), a composite indicator of income, educational attainment, and fertility. Data collected from 1990 to 2017 on children and adolescents from birth through 19 years of age in 195 countries and territories were assessed. Data analysis occurred from January 2018 to August 2018.
Exposures: Being under the age of 20 years between 1990 and 2017.
Main Outcomes and Measures: Death and disability. All-cause and cause-specific deaths, disability-adjusted life years, years of life lost, and years of life lived with disability.
Results: Child and adolescent deaths decreased 51.7% from 13.77 million (95% uncertainty interval [UI], 13.60-13.93 million) in 1990 to 6.64 million (95% UI, 6.44-6.87 million) in 2017, but in 2017, aggregate disability increased 4.7% to a total of 145 million (95% UI, 107-190 million) years lived with disability globally. Progress was uneven, and inequity increased, with low-SDI and low-middle-SDI locations experiencing 82.2% (95% UI, 81.6%-82.9%) of deaths, up from 70.9% (95% UI, 70.4%-71.4%) in 1990. The leading disaggregated causes of disability-adjusted life years in 2017 in the low-SDI quintile were neonatal disorders, lower respiratory infections, diarrhea, malaria, and congenital birth defects, whereas neonatal disorders, congenital birth defects, headache, dermatitis, and anxiety were highest-ranked in the high-SDI quintile.
Conclusions and Relevance: Mortality reductions over this 27-year period mean that children are more likely than ever to reach their 20th birthdays. The concomitant expansion of nonfatal health loss and epidemiological transition in children and adolescents, especially in low-SDI and middle-SDI countries, has the potential to increase already overburdened health systems, will affect the human capital potential of societies, and may influence the trajectory of socioeconomic development. Continued monitoring of child and adolescent health loss is crucial to sustain the progress of the past 27 years.
Fulltext Do domestic innovations promote trade openness? Empirical evidence from emerging economies

Khan MN, Jan AA, Asif M, Lai FW, Shad MK, Shadab S

Heliyon, 2023 Dec;9(12):e22848.
PMID: 38076083 DOI: 10.1016/j.heliyon.2023.e22848

PURPOSE: Innovation activities have gained much importance due to their pivotal role in achieving economic growth - directly by increasing productivity and - indirectly by increasing the degree of trade openness. This study aims to focus on the indirect channel, a rarely explored area of research, especially in the context of emerging economies.
METHODOLOGY: To achieve the aim of the study, four proxies of innovation (resident patent applications, nonresident patent applications, scientific and technical journal articles, and research and development expenditures) are used to establish a robust relationship between innovation activities and trade openness in BRICS economies. Panel data from 2000 to 2020 is obtained from World Development Indicators and Penn World Tables. Econometric techniques of panel data such as fixed effect and generalized least squares are employed to extract results from the specified models.
FINDINGS: The findings of the study revealed that three proxies of innovation (i.e., resident patent applications, nonresident patent applications, scientific and technical journal articles) have a significant positive role in improving trade openness in the BRICS economies. However, the fourth proxy of innovation i.e., research and development expenditures had a negative impact on the degree of trade openness. Besides, innovation activities such as inflation rate and foreign direct investment have also influenced the degree of trade openness positively and significantly. Conversely, GDP per capita had a negative relationship with trade openness. Moreover, domestic investments showed a positive influence on the degree of trade openness while employment had a negative and insignificant influence on the degree of trade openness. Finally, the causality analysis revealed a one-way relationship running from innovations to trade openness.
IMPLICATIONS: In view of the results obtained, the policymakers of the BRICS economies might focus on encouraging innovation activities to enhance the degree of trade openness. Increased trade openness will consequently contribute to economic growth enormously and thus the attainment of sustainable development goals (SDG-8). Policymakers are also suggested to encourage FDI inflows and further ensure a moderate inflation rate to improve the degree of trade openness and hence accelerate economic growth.
ORIGINALITY: This study focused on examining the nexus between innovation activities and trade openness in emerging economies, which is indeed an interesting but rarely explored area of research. The findings of the study might help the policymakers of the BRICS economies in formulating policies regarding trade openness and innovation activities.
Does foreign direct investment influence carbon emission-related environmental problems? Contextual evidence from developing countries across Sub-Saharan Africa

Khan MN, Shahbaz M, Murshed M, Khan S, Hosen M

Environ Sci Pollut Res Int, 2024 Feb 19.
PMID: 38372919 DOI: 10.1007/s11356-024-32276-3

Sub-Saharan African nations face multifaceted environmental problems, especially those associated with carbon discharges. Hence, this study calculates a composite carbon index in the context of 39 developing nations from this region and uses it as a proxy for the carbon emission-related environmental problems they have faced during the 2000-2020 period. This index is estimated by utilizing data regarding annual carbon dioxide discharges, output-based carbon productivity rates, and energy consumption-based carbon intensity levels in the concerned countries. Hence, policy takeaways from this study have critical relevance for the selected sub-Saharan African nations to help them achieve the objectives related to the Sustainable Development Goals agenda and the Paris Accord. Overall, the findings from the econometric analyses verify that more receipt of foreign direct investment initially raises but later on reduces environmental problems. Thus, the nexus concerning these variables depicts an inverse U-shape. Besides, the results endorse that greening the energy consumption structures of the sampled sub-Saharan African countries helps to abate their environmental problems in the long run while financial development aggravates the extent of environmental adversities that take place. Lastly, improving the quality of regulatory agencies enables the Sub-Saharan African nations to further mitigate their environmental problems. Moreover, these aforementioned findings are observed to be heterogeneous across low- and middle-income categories of the selected Sub-Saharan African countries. Furthermore, the heterogeneity of the findings is also confirmed by the outcomes derived from the country-specific analyses. Nevertheless, these nations should attract clean energy-embodying foreign direct investment, make their energy consumption structures greener by amplifying renewable energy adoption rates, introduce green funds to develop their financial sectors, and make their environmental regulatory agencies more transparent with their activities.
Effects of

Khan MN, Arifin Z, Ismail E, Ali SF

J Org Chem, 2000 Mar 10;65(5):1331-4.
PMID: 10814092

Effects of cetyltrimethylammonium bromide (CTABr) micelles on second-order rate constants (k(n)(obs)) for nucleophilic reactions of amines (piperidine and n-butylamine) with ionized phenyl salicylate (PS(-)) reveal a nonlinear decrease with the increase in [D(n)] (where [D(n)] = [CTABr](T) - cmc) at a constant [NaBr] and 35 degrees C. The observed data, at a constant [NaBr], fit reasonably well to a pseudophase model of micelles, and such a data fit gives kinetic parameters such as CTABr micellar binding canstant (K(S)) of PS(-). The effect of [NaBr] upon K(S) is explained with the empirical relationship K(S) = K(S)(0)/(1 + psi[NaBr]), where psi is an empirical parameter.
Effects of Nonionic and Mixed Cationic-Nonionic Micelles on the Rate of Alkaline Hydrolysis of 4-Nitrophthalimide

Khan MN, Ismail E

J Colloid Interface Sci, 2001 Aug 15;240(2):636-639.
PMID: 11482975

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 4-nitrophthalimide show a monotonic decrease with increase in [C(12)E(23)](T) (total concentration of Brij 35) at constant [CH(3)CN] and [NaOH]. This micellar effect is explained in terms of a pseudophase micelle model. The rate of hydrolysis becomes too slow to monitor at [C(12)E(23)](T)>/=0.03 M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C(12)E(23)](T)>/=0.04 M in the presence of 0.006-0.02 M CTABr at 0.01 M NaOH. The plots of k(obs) versus [C(12)E(23)](T) show minima at 0.006 and 0.01 M CTABr, while such a minimum is not visible at 0.02 M CTABr. Copyright 2001 Academic Press.
Effects of Nonionic, Cationic, and Mixed Nonionic-Cationic Surfactants on the Acid-Base Behavior of Phenyl Salicylate

Khan MN, Arifin Z, Yusoff MR, Ismail E

J Colloid Interface Sci, 1999 Dec 15;220(2):474-476.
PMID: 10607470

The effects of Brij 35 micelles, CTABr micelles, and mixed Brij 35-CTABr micelles on the acid-base behavior of phenyl salicylate (PST) have been studied in aqueous solution containing 2% v/v acetonitrile. The apparent pK(b) (pK(app)(b)) of PST is decreased by 1.5 pK units with the increase in [Brij 35] from 0 to 0.02 M which is attributed to micellar medium effect. The values of pK(app)(b) remain almost independent of [CTABr] within its range 0.01-0.03 M. The increase in [CTABr] from 0 to 0.03 M in aqueous solution containing 0.02 M Brij 35 has not resulted in a change in pK(app)(b). This shows that the characeristic structural features of nonionic Brij 35 micelles remain essentially unchanged on addition of CTABr under the present experimental conditions. Copyright 1999 Academic Press.
Effects of [NaBr] on the rate of intramolecular general base-assisted hydrolysis of n-(2'-hydroxyphenyl)phthalimide in the presence of cationic micelles: kinetic evidence for the probable micellar structural transition

Khan MN, Azri MH

J Phys Chem B, 2010 Jun 24;114(24):8089-99.
PMID: 20509705 DOI: 10.1021/jp102109q

Pseudofirst-order rate constants for aqueous cleavage of N-(2'-hydroxyphenyl)phthalimide (1), obtained at 0.001 M NaOH, 2 x 10(-4) M 1, 2% v/v CH(3)CN, and 30 degrees C, show a nonmonotonic decrease with the increase in the total concentration of cetyltrimethylammonium bromide ([CTABr](T)) within its range >/=9 x 10(-5)-or=0.04 M CTABr and within a [NaBr] range of 0.0-0.005 M. These observations, in view of the pseudophase (PP) model of the micelle, reveal the presence of presumably spherical micelles at or=4 x 10(-4) M causes a micellar structural transition from most likely spherical to cylindrical, which is evident from the increase in K(S) values from 3.46 x 10(3) to 11.4 x 10(3) M(-1) with the increase in [CTABr](T) from 4 x 10(-4) to approximately 1 x 10(-3) M in the absence of NaBr. The values of k(obs) at different [NaBr] and at a constant [CTABr](T) follow a kinetic relationship derived from an empirical equation coupled with a PP model of micelle. This relationship gives the value of a kinetic parameter, F(X/S), which represents the fraction of micellized S(-) (S(-) = 1(-)) transferred to the aqueous phase by the limiting concentration of X(-) (X(-) = Br(-)) through ion exchange X(-)/S(-). The value of F(Br/1) is 0.65 +/- 0.12.
Effects of [NaOH] and [KBr] on Intramolecular General Base-Catalyzed Methanolysis of Ionized Phenyl Salicylate in the Presence of Cationic Micelles

Khan MN

J Org Chem, 1997 May 16;62(10):3190-3193.
PMID: 11671702

Pseudo-first-order rate constants obtained for methanolysis of ionized phenyl salicylate (PS(-)) at constant [MeOH], [MeCN], [NaOH] or [KOH], and [KBr] and at 35 degrees C show a decrease with the increase in [CTABr] (where CTABr represents cetyltrimethylammonium bromide) from 0.0-0.01 M. These observed data obey a pseudophase model of the micelle. The micellar binding constants (K(S)) of PS(-), pseudo-first-order rate constants (k(M)) for methanolysis of PS(-) in the micellar pseudophase and cmc are almost unchanged with the change in [NaOH] from 0.005-0.050 M. The increase in [KBr] from 0.0 to 0.3 M at 0.01 M KOH decreases K(S) from 5140 to 653 M(-)(1) and cmc from 1.9 x 10(-)(4) to 0.2 x 10(-)(4) M. Pseudo-first-order rate constants, k(M), are almost independent of [KBr] at 0.01 M KOH.
Fulltext Efficacy of Naphthyl Acetic Acid Foliar Spray in Moderating Drought Effects on the Morphological and Physiological Traits of Maize Plants (Zea mays L.)

Ullah S, Khan MI, Khan MN, Ali U, Ali B, Iqbal R, et al.

ACS Omega, 2023 Jun 13;8(23):20488-20504.
PMID: 37323381 DOI: 10.1021/acsomega.3c00753

The threat of varying global climates has greatly driven the attention of scientists, as climate change increases the odds of worsening drought in many parts of Pakistan and the world in the decades ahead. Keeping in view the forthcoming climate change, the present study aimed to evaluate the influence of varying levels of induced drought stress on the physiological mechanism of drought resistance in selected maize cultivars. The sandy loam rhizospheric soil with moisture content 0.43-0.5 g g-1, organic matter (OM) 0.43-0.55 g/kg, N 0.022-0.027 g/kg, P 0.028-0.058 g/kg, and K 0.017-0.042 g/kg was used in the present experiment. The findings showed that a significant drop in the leaf water status, chlorophyll content, and carotenoid content was linked to an increase in sugar, proline, and antioxidant enzyme accumulation at p < 0.05 under induced drought stress, along with an increase in protein content as a dominant response for both cultivars. SVI-I & II, RSR, LAI, LAR, TB, CA, CB, CC, peroxidase (POD), and superoxide dismutase (SOD) content under drought stress were studied for variance analysis in terms of interactions between drought and NAA treatment and were found significant at p < 0.05 after 15 days. It has been found that the exogenous application of NAA alleviated the inhibitory effect of only short-term water stress, but yield loss due to long-term osmotic stress will not be faced employing growth regulators. Climate-smart agriculture is the only approach to reduce the detrimental impact of global fluctuations, such as drought stress, on crop adaptability before they have a significant influence on world crop production.
Efficient rate enhancement due to intramolecular general base (IGB) assistance in the hydrolysis of N-(o-hydroxyphenyl)phthalimide

Sim YL, Ariffin A, Khan MN

J Org Chem, 2007 Mar 30;72(7):2392-401.
PMID: 17341117

The rates of the hydrolyses of N-(o-hydroxyphenyl)phthalimide (1) and N-(o-methoxyphenyl)phthalimide (2), studied at different pH, show that the hydrolysis of 1 involves intramolecular general base (IGB) assistance where the o-O- group of ionized 1 acts as IGB and H2O as the reactant. The rate enhancement due to the IGB-assisted reaction of H2O with ionized 1 is>8x10(4)-fold. Pseudo-first-order rate constant for the reaction of water with 2 is approximately 2x10(3)-fold smaller than the first-order rate constant (0.10 s-1) for pH-independent hydrolysis of 1 within the pH range of 9.60-10.10. Second-order rate constants (kOH) for hydroxide ion-assisted hydrolysis of ionized 1 and 2 are 3.0 and 29.1 M-1 s-1, respectively. The solvent deuterium kinetic isotope effect (dKIE) on the rate of alkaline hydrolysis of 1 and 2 reveals that the respective values of kOH/kOD are 0.84 and 0.78, where kOD represents the second-order rate constant for DO--assisted cleavage of these imides (1 and 2). The value of kwH2O/kdD2O is 2.04, with kwH2O and kdD2O representing pseudo-first-order rate constants for the reactions of ionized 1 with H2O and D2O, respectively.

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