A three-state mechanism for trifluoroethanol denaturation of an intrinsically disordered protein (IDP).

Relating the amino acid composition and sequence to chain folding and binding preferences of intrinsically disordered proteins (IDPs) has emerged as a huge challenge. While globular proteins have respective 3D structures that are unique to their individual functions, IDPs violate this structure-function paradigm because rather than having a well-defined structure an ensemble of rapidly interconverting disordered structures characterize an IDP. This work measures 2,2,2-trifluoroethanol (TFE)-induced equilibrium transitions of an IDP called AtPP16-1 (Arabidopsis thaliana phloem protein type 16-1) by using fluorescence, circular dichroism, infrared and nuclear magnetic resonance (NMR) methods at pH 4, 298 K. Low TFE reversibly removes the tertiary structure to produce an ensemble of obligate intermediate ($\mathrm{I}$) retaining the native-state ($\mathrm{N}$) secondary structure. The intermediate $\mathrm{I}$ is preceded by a non-obligate tryptophan-specific intermediate ${\mathrm{I}}_{\mathrm{w}}$ whose population is detectable for AtPP16-1 specifically. Accumulation of such non-obligate intermediates is discriminated according to the sequence composition of the protein. In all cases, however, a tertiary structure-unfolded general obligate intermediate $\mathrm{I}$ is indispensable. The $\mathrm{I}$ ensemble has higher helical propensity conducive to the acquisition of an exceedingly large level of α-helices by a reversible denaturation transition of $\mathrm{I}$ to the denatured state $\mathrm{D}$ as the TFE level is increased. Strikingly, it is the same $\mathrm{N}\rightleftharpoons \mathrm{I}\rightleftharpoons \mathrm{D}$ scheme typifying the TFE transitions of globular proteins. The high-energy state $\mathrm{I}$ characterized by increased helical propensity is called a universal intermediate encountered in both genera of globular and disordered proteins. Neither $\mathrm{I}$ nor $\mathrm{D}$ strictly show molten globule (MG)-like properties, dismissing the belief that TFE promotes MGs.

Molecular and genetic perspectives of cold tolerance in wheat.

Environmental variation is the most crucial problem as it is causing food insecurity and negatively impacts food availability, utilization, assessment, and stability. Wheat is the largest and extensively cultivated staple food crop for fulfilling global food requirements. Abiotic stresses including salinity, heavy metal toxicity, drought, extreme temperatures, and oxidative stresses being the primary cause of productivity loss are a serious threat to agronomy. Cold stress is a foremost ecological constraint that is extremely influencing plant development, and yield. It is extremely hampering the propagative development of plant life. The structure and function of plant cells depend on the cell's immune system. The stresses due to cold, affect fluid in the plasma membrane and change it into crystals or a solid gel phase. Plants being sessile in nature have evolved progressive systems that permit them to acclimatize the cold stress at the physiological as well as molecular levels. The phenomenon of acclimatisation of plants to cold stress has been investigated for the last 10 years. Studying cold tolerance is critical for extending the adaptability zones of perennial grasses. In the present review, we have elaborated the current improvement of cold tolerance in plants from molecular and physiological viewpoints, such as hormones, the role of the posttranscriptional gene, micro RNAs, ICE-CBF-COR signaling route in cold acclimatization and how they are stimulating the expression of underlying genes encoding osmoregulatory elements and strategies to improve cold tolerance in wheat.

Mechanical Unfolding and Amorphous Aggregation of Protein in a Very Low DC Field.

A common theme for the effect of electric field on the structure and conformation of proteins is lacking due to a myriad of conflicting reports emerging from different protein systems subjected to different frequencies and strengths of the field (0.8 -108 V cm-1), which may be pulsed for a few nano- to microseconds or applied continuously up to several hours. It is however necessary to find a common theme because of the increasing use of electric field not only to understand Stark-like electro-optic effects in large molecules but also in food processing technology, and perhaps in the disruption of amyloid bodies in Alzheimer's condition. This study finds an optimized condition of 1.3 V cm-1 DC field, in which the electrophoretic mobility is ∼1.2 mm h-1, and systematically shows electrophoretic, electrochemical, and unfolding effects at different levels of cytochrome c structure within ∼90 min of turning the field on. Interestingly, the protein undergoes amorphous aggregation concomitant with a high degree of denaturation. In support of this suggestion, data for myoglobin and trypsin are also presented. Effort has been made to separate out the chemical and physical effects of the electric field.

The Blending Effect of Single-Shade Composite with Different Shades of Conventional Resin Composites-An In Vitro Study.

OBJECTIVES: Single-shade composite systems are gaining popularity among clinicians due to the claimed potential of blending with different tooth structure shades while restoring the tooth. The purpose of this study was to evaluate the blending effect of two single-shade composite with different shades of conventional resin composite systems. MATERIALS AND METHODS: Seventy-two composite cylinders of B1, B2, A1, A2, A3, or A3.5 shade from CharmFil Plus (CP) and Filtek Universal Restorative (3M) were prepared using custom-made silicone mold. Single-shade composite OMNICHROMA (OC) or Beautifil II Enamel (BE) was placed in the center of each cylinder and polymerized. The color parameters, lightness (L*), chroma (C*), and hue (H*) of each composite were measured using a color chronometer. Furthermore, color stability of the samples was evaluated after 1-week staining challenge. STATISTICAL ANALYSIS: Multivariant analysis was performed to evaluate the effect of material and shade on the color parameters. Multiple comparisons of the data were performed using post hoc test. The staining challenge data were analyzed using repeated measure analysis of variance and paired sample T-test. RESULTS: The multivariant analysis showed a statistically significant difference in color parameters among CP, 3M, OC, and BE (p = 0.001). Image analysis showed a visual blending effect for both OC and BE for certain shades; however, some color contrast with the darker shades was observed. The C* value of OC showed a similar pattern to CP; however, the H* of the latter was closely followed by BE. The L* value showed statistically significant difference among the shades of 3M, and in OC and BE when blended with 3M. CONCLUSION: All four materials used in this study showed color alteration after the staining challenge. Single-shade composite can blend with only certain shades of resin composites.

A surprisingly simple three-state generic process for reversible protein denaturation by trifluoroethanol.

Despite the rich knowledge of the influence of 2,2,2-trifluoroethanol (TFE) on the structure and conformation of peptides and proteins, the mode(s) of TFE-protein interactions and the mechanism by which TFE reversibly denatures a globular protein remain elusive. This study systematically examines TFE-induced equilibrium transition curves for six paradigmatic globular proteins by using basic fluorescence and circular dichroism measurements under neutral pH conditions. The results are remarkably simple. Low TFE invariably unfolds the tertiary structure of all proteins to produce the obligate intermediate (I) which retains nearly all of native-state secondary structure, but enables the formation of extra α-helices as the level of TFE is raised higher. Inspection of the transitions at once reveals that the tertiary structure unfolding is always a distinct process, necessitating the inclusion of at least one obligate intermediate in the TFE-induced protein denaturation. It appears that the intermediate in the minimal unfolding mechanism N⇌I⇌D somehow acquires higher α-helical propensity to generate α-helices in excess of that in the native state to produce the denatured state (D), also called the TFE state. The low TFE-populated intermediate I may be called a universal intermediate by virtue of its α-helical propensity. Contrary to many earlier suggestions, this study dismisses molten globule (MG)-like attribute of I or D.

Evaluation of the efficacy of different sources of omega-3 fatty acids in polycystic ovarian syndrome (PCOS) induced rats.

The study was planned to check the beneficial effects of various sources of omega-3 fatty acids (synthetic, flaxseed oil, fish oil) on 45 Wistar female rats. The rats were divided into five groups and assigned to different diets i.e. NC (Negative control), PC (Positive control), SO (Synthetic omega-3 250mg/kg/orally/daily), FO (flaxseed oil 250mg/kg/orally/daily) and F (fish oil 250mg/kg/orally/diet). Animals fed on different diets were induced PCOS by an intramuscular (IM) injection of estradiol-valerate (4mg/rat/IM) except NC group. Results of the lipid profile indicated that F showed highest increase in HDL level (35.67±1.45), while cholesterol, LDL, triglycerides, blood glucose and body weight were reduced in all three treatment groups. In case of a hormonal profile, testosterone, luteinizing hormone (LH) and insulin levels showed a significant reduction after treatments. It can be concluded form the study that different sources of omega-3 fatty acids can be a new approach to treat the symptoms of PCOS.

Complete observation of all structural, conformational, and fibrillation transitions of monomeric globular proteins at submicellar sodium dodecyl sulfate concentrations.

Although considerable information is available regarding protein-sodium dodecyl sulfate (SDS) interactions, it is still unclear as to how much SDS is needed to denature proteins. The role of protein charge and micellar surfactant concentration on amyloid fibrillation is also unclear. This study reports on equilibrium measurements of SDS interaction with six model proteins and analyzes the results to obtain a general understanding of conformational breakdown, reorganization and restructuring of secondary structure, and entry into the amyloid fibrillar state. Significantly, all of these responses are entirely resolved at much lower than the critical micellar concentration (CMC) of SDS. Electrostatic interaction of the dodecyl sulfate anion (DS- ) with positive surface potential on the protein can completely unfold both secondary and tertiary structures, which is followed by protein chain restructuration to α-helices. All SDS-denatured proteins contain more α-helices than the corresponding native state. SDS interaction stochastically drives proteins to the aggregated fibrillar state.

Effects of inosine 5'-monophosphate supplementation in high fishmeal and high soybean diets on growth, immune-related gene expression in gibel carp (Carassius auratus gibelio var. CAS â ¢), and its challenge against Aeromonas hydrophila infection.

The present study was conducted to evaluate dietary inosine 5'-monophosphate (5'-IMP) on growth, immune genes expression and disease resistance against Aeromonas hydrophila in juvenile gibel carp (Carassius auratus gibelio var. CAS Ⅲ) (initial body weight: 7.48 g). Six diets were formulated containing exogenous 5'-IMP at three gradient levels (0, 0.1% and 0.2%) in the high dietary fishmeal group (15% fishmeal: D1, D2, D3) and in the high dietary soybean meal group (33% soybean meal: D4, D5, D6). Each diet was randomly allotted to triplicate tanks in a recirculating system. After the feeding trial, fish were exposed to Aeromonas hydrophila challenge. Hematological and immunological responses were analyzed before and after challenge. The results indicated that feeding rate in all 5'-IMP supplemented treatments (D2, D3, D5 and D6) and daily growth coefficient in D5 and D6 were reduced compared with those of respective control treatments (D1 and D4) without 5'-IMP addition (P < 0.05). The cumulative survival rates were numerically improved by dietary 5'-IMP supplementation (P > 0.05). Compared with the respective control treatment, in the high fishmeal group, plasma SOD and MPO were significantly elevated in D3 at the end of feeding trial (P < 0.05), plasma SOD and lysozyme were significantly increased in D3 after bacterial challenge (P < 0.05); in high soybean meal group, plasma lysozyme activity was significantly elevated in D5 post bacterial challenge (P < 0.05). Most of the expression of immune related genes (intelectin, major histocompatibility complex class II ß (MHC II ß), Complement 3 (C3), Complement component C7-1 (ccC7), lysozyme C, Interleukin 1ß (IL-1ß), Tumor necrosis factor α1 (TNF-α1), Transforming growth factor-beta (TGF-ß) and Interleukin 8 (IL-8)) in spleen, kidney and liver of the fish were significantly affected by supplementation of 5'-IMP at the end of feeding trial and post bacterial challenge. Additionally, adding 5'-IMP in high soybean meal diets exerted further effects of promoting immunity than counterparts in high fishmeal diets. Considering enhanced disease resistance, the immunopotentiation of 5'-IMP was manifested when the addition level was 0.1% in high soybean meal diets and 0.2% in high fishmeal diets.