Reversible inactivation and dissociation of glutamine synthetase of Neurospora crassa by urea

1971 ◽  
Vol 17 (4) ◽  
pp. 451-459 ◽  
Author(s):  
G. W. Ward ◽  
M. Kapoor
Keyword(s):  
Glutamine Synthetase ◽  
Protective Effect ◽  
Neurospora Crassa ◽  
The State ◽  
Native State ◽  
Reversible Inactivation ◽  
Partial Inactivation ◽  
Partially Unfolded ◽  
The Stability

The effect of urea on the stability and the state of aggregation of glutamine synthetase is reported. Substrates and modulators of this enzyme exert a protective effect against urea-induced loss of activity. On partial inactivation by urea, the enzyme appears to consist of a dimeric species and an intermediate, partially unfolded form. Subsequent to the removal of urea, the presence of substrates and effectors is necessary to bring about a reversal of inactivation and a return of the enzyme lo the native or near-native state.

scholarly journals Folding pathway of the pyridoxal 5′-phosphate C-S lyase MalY from Escherichia coli

2005 ◽  
Vol 389 (3) ◽  
pp. 885-898 ◽  
Author(s):  
Mariarita Bertoldi ◽  
Barbara Cellini ◽  
Douglas V. Laurents ◽  
Carla Borri Voltattorni
Keyword(s):  
Escherichia Coli ◽  
Gel Filtration ◽  
Native State ◽  
Equilibrium Conditions ◽  
Lyase Activity ◽  
Three Stages ◽  
Soluble Aggregates ◽  
Equilibrium Transition ◽  
Partially Unfolded ◽  
The Stability

MalY from Escherichia coli is a bifunctional dimeric PLP (pyridoxal 5′-phosphate) enzyme acting as a β-cystathionase and as a repressor of the maltose system. The spectroscopic and molecular properties of the holoenzyme, in the untreated and NaBH4-treated forms, and of the apoenzyme have been elucidated. A systematic study of the urea-induced unfolding of MalY has been monitored by gel filtration, cross-linking, ANS (8-anilino-1-naphthalenesulphonic acid) binding and by visible, near- and far-UV CD, fluorescence and NMR spectroscopies under equilibrium conditions. Unfolding proceeds in at least three stages. The first transition, occurring between 0 and 1 M urea, gives rise to a partially active dimeric species that binds PLP. The second equilibrium transition involving dimer dissociation, release of PLP and loss of lyase activity leads to the formation of a monomeric equilibrium intermediate. It is a partially unfolded molecule that retains most of the native-state secondary structure, binds significant amounts of ANS (a probe for exposed hydrophobic surfaces) and tends to self-associate. The self-associated aggregates predominate at urea concentrations of 2–4 M for holoMalY. The third step represents the complete unfolding of the enzyme. These results when compared with the urea-induced unfolding profiles of apoMalY and NaBH4-reduced holoenzyme suggest that the coenzyme group attached to the active-site lysine residue increases the stability of the dimeric enzyme. Both holo- and apo-MalY could be successfully refolded into the active enzyme with an 85% yield. Further refolding studies suggest that large misfolded soluble aggregates that cannot be refolded could be responsible for the incomplete re-activation.

scholarly journals The Conformational Stabilities of Tropomyosins

1976 ◽  
Vol 29 (6) ◽  
pp. 405 ◽  
Author(s):  
EF Woods
Keyword(s):  
Guanidine Hydrochloride ◽  
Coiled Coil ◽  
Helical Structure ◽  
Globular Proteins ◽  
Free Energies ◽  
Native State ◽  
Denatured State ◽  
Partially Unfolded ◽  
The Stability ◽  
Partially Unfolded States

The stability to denaturation by heat and guanidine hydrochloride of seven vertebrate (including skeletal, cardiac and smooth muscle) tropomyosins and three invertebrate tropomyosins was examined. The transition profiles were discontinuous and in many cases distinct plateaux were observed which indicated the presence of unique partially unfolded states at intermediate temperatures and guanidine hydrochloride concentrations. The denaturation by guanidine hydrochloride could be described in the majority of cases by a model in which the native state unfolds to a partially unfolded stable intermediate which then unfolds to the completely denatured state. On this basis it was possible to estimate the free energies of unfolding in water. It was shown that part of the IX-helical structure of tropomyosin is only marginally stable and the free energy of unfolding in water of this segment is less than values found for globular proteins, whereas another segment (or segments) has a stability comparable to that found for globular proteins. The stepwise unfolding may be explained in terms of the coiled-coil interactions in tropomyosin.

Cracking national integration after the events (the Arab Spring) and its impact On regional stability

2019 ◽  
Vol 3 (6) ◽  
pp. 1
Author(s):  
Muhannad Al Janabi Al Janabi
Keyword(s):  
Arab Spring ◽  
The State ◽  
The Political ◽  
Prominent Feature ◽  
Regional Stability ◽  
National Integration ◽  
Arab Region ◽  
Political Media ◽  
The Stability ◽  
The Arab Spring

Since late 2010 and early 2011, the Arab region has witnessed mass protests in Tunisia, Egypt, Libya, Syria, Yemen, Iraq, Bahrain and other countries that have been referred to in the political, media and other literature as the Arab Spring. These movements have had a profound effect on the stability of the regimes Which took place against it, as leaders took off and contributed to radical reforms in party structures and public freedoms and the transfer of power, but it also contributed to the occurrence of many countries in an internal spiral, which led to the erosion of the state from the inside until it became a prominent feature of the Arab) as is the case in Syria, Libya, Yemen and Iraq.

IMPACT OF GOVERNMENT DEBT ON FINANCIAL SECURITY OF UKRAINE

2017 ◽  
Author(s):  
Olena Pikaliuk ◽  
◽  
Dmitry Kovalenko ◽  
Keyword(s):  
Economic Development ◽  
Public Debt ◽  
Positive Impact ◽  
The State ◽  
Financial Security ◽  
State Budget ◽  
The Public ◽  
Debt Security ◽  
The Stability ◽  
The Impact

One of the main criteria for economic development is the size of the public debt and its dynamics. The article considers the impact of public debt on the financial security of Ukraine. The views of scientists on the essence of public debt and financial security of the state are substantiated. An analysis of the dynamics and structure of public debt of Ukraine for 2014-2019. It is proved that one of the main criteria for economic development is the size of public debt and its dynamics. State budget deficit, attracting and using loans to cover it have led to the formation and significant growth of public debt in Ukraine. The volume of public debt indicates an increase in the debt security of the state, which is a component of financial security. Therefore, the issue of the impact of public debt on the financial security of Ukraine is becoming increasingly relevant. The constant growth and large amounts of debt make it necessary to study it, which will have a positive impact on economic processes that will ensure the stability of the financial system and enhance its security.

scholarly journals Nanoencapsulation of Pomegranate Extract to Increase Stability and Potential Dermatological Protection

Pharmaceutics ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 271
Author(s):  
Lucía Yepes-Molina ◽  
José A. Hernández ◽  
Micaela Carvajal
Keyword(s):  
Oxidative Stress ◽  
Heavy Metals ◽  
Protective Effect ◽  
Uv Radiation ◽  
Entrapment Efficiency ◽  
Hacat Cells ◽  
Biotechnological Applications ◽  
Accelerated Stability ◽  
The Stability ◽  
Brassica Oleracea L

Pomegranate extract (PG-E) has been reported to exert a protective effect on the skin due to its antioxidant activity. Ingredients rich in phenolic compounds are unstable in extract solutions, and, therefore, the use of a suitable nanosystem to encapsulate this type of extract could be necessary in different biotechnological applications. Thus, we investigated the capacity of Brassica oleracea L. (cauliflower) inflorescence vesicles (CI-vesicles) to encapsulate PG-E and determined the stability and the antioxidant capacity of the system over time. In addition, the protective effect against UV radiation and heavy metals in HaCaT cells was also tested. The CI-vesicles had an entrapment efficiency of around 50%, and accelerated stability tests did not show significant changes in the parameters tested. The results for the HaCaT cells showed the non-cytotoxicity of the CI-vesicles containing PG-E and their protection against heavy metals (lead acetate and mercuric chloride) and UV-B radiation through a reduction of oxidative stress. The reduction of the percentage of deleted mtDNA (mtDNA4977, “common deletion”) in UV-treated HaCaT cells due to the presence of CI-vesicles containing PG-E indicated the mechanism of protection. Therefore, the effects of CI-vesicles loaded with PG-E against oxidative stress support their utilization as natural cosmeceuticals to protect skin health against external damage from environmental pollution and UV radiation.

Cold Shock Domain of the Human Y-Box Protein YB-1. Backbone Dynamics and Equilibrium between the Native State and a Partially Unfolded State†

Biochemistry ◽  
2004 ◽  
Vol 43 (31) ◽  
pp. 10237-10246 ◽  
Author(s):  
Cathelijne P. A. M. Kloks ◽  
Marco Tessari ◽  
Geerten W. Vuister ◽  
Cornelis W. Hilbers
Keyword(s):  
Cold Shock ◽  
Backbone Dynamics ◽  
Native State ◽  
Unfolded State ◽  
Cold Shock Domain ◽  
Partially Unfolded

Zambia's Second Republic —the Establishment of a One-Party State

1974 ◽  
Vol 12 (2) ◽  
pp. 231-244 ◽  
Author(s):  
Jan Pettman
Keyword(s):  
Political Development ◽  
Political System ◽  
The State ◽  
Second Republic ◽  
National Unity ◽  
Common Enemy ◽  
The Common ◽  
The Government ◽  
The Stability ◽  
Party State

Zambia inherited a system of government and administration in 1964 which was ill-suited to the tasks of political development to which her new leaders were dedicated. What little national unity and mobilisation had been achieved in the independence struggle declined with the removal of the common enemy. The Government rested on a fragile base, without the support of agreed rules and practices to limit and contain conflict, and without adequate instruments available for the implementation of its policies. So the search began for a more suitable political system, which could cope with the new needs of independence, and provide for the stability of the state and the survival of the Government.

Cultivating the Art of Anxiety: Securitising Culture in China

China Report ◽  
2021 ◽  
pp. 000944552110470
Author(s):  
Rudolf Fürst
Keyword(s):  
Ethnic Minorities ◽  
Security Policy ◽  
Political Leadership ◽  
The State ◽  
Public Communication ◽  
The Political ◽  
Xi Jinping ◽  
The Public ◽  
The Stability ◽  
Security Concern

Deepening globalisation and worldwide availability of free information and ideas raise concerns of the communist China’s political leadership about the stability of the regime and the sustainability of the state ideological orthodoxy. Therefore, the state’s tightening control of the public communication to curtail the domestic criticism and occasional public discontent is becoming framed and legitimised in terms of cultural security as a non-traditional security concern. This study argues that the restrictive impacts of the politicisation of culture in the centralised agenda of President Xi Jinping reinvigorate China’s anti-Western narratives and attitudes. The research focuses on the state’s cultural security-related and applicable strategy in the political and institutional agenda and media. Moreover, the study also traces the state cultural security policy in the field of the civic and non-governmental sector, religious and ethnic minorities policy, literature, film and audiovisual sectors. The findings assess the concern that the intellectually anachronistic, self-restraining and internationally hostile policy devaluates China’s cultural potential and complexity.

Robust active disturbance attenuation control of an uncertain quadrotor

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nigar Ahmed ◽  
Ajeet kumar Bhatia ◽  
Syed Awais Ali Shah
Keyword(s):  
Control Algorithm ◽  
Sliding Mode ◽  
The State ◽  
Disturbance Attenuation ◽  
State Variables ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Content Type ◽  
Highly Nonlinear ◽  
The Stability

PurposeThe aim of this research is to design a robust active disturbance attenuation control (RADAC) technique combined with an extended high gain observer (EHGO) and low pass filter (LPF).Design/methodology/approachFor designing a RADAC technique, the sliding mode control (SMC) method is used. Since the standard method of SMC exhibits a chattering phenomenon in the controller, a multilayer sliding mode surface is designed for avoiding the chattering. In addition, to attenuate the unwanted uncertainties and disturbances (UUDs), the techniques of EHGO and LPF are deployed. Besides acting as a patch for disturbance attenuation, the EHGO design estimates the state variables. To investigate the stability and effectiveness of the designed control algorithm, the stability analysis followed by the simulation study is presented.FindingsThe major findings include the design of a chattering-free RADAC controller based on the multilayer sliding mode surface. Furthermore, a criterion of integrating the LPF scheme within the EHGO scheme is also developed to attenuate matched and mismatched UUDs.Practical implicationsIn practice, the quadrotor flight is opposed by different kinds of the UUDs. And, the model of the quadrotor is a highly nonlinear underactuated model. Thus, the dynamics of the quadrotor model become more complex and uncertain due to the additional UUDs. Hence, it is necessary to design a robust disturbance attenuation technique with the ability to estimate the state variables and attenuate the UUDs and also achieve the desired control objectives.Originality/valueDesigning control methods to attenuate the disturbances while assuming that the state variables are known is a common practice. However, investigating the uncertain plants with unknown states along with the disturbances is rarely taken in consideration for the control design. Hence, this paper presents a control algorithm to address the issues of the UUDs as well as investigate a criterion to reduce the chattering incurred in the controller due to the standard SMC algorithm.

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