7 19 where is my water

This study also provided two crucial insights concerning water movement. First, water molecules cannot directly permeate from one side of the OEC to the other Fig. However, this finding did not exclude the possibility for water to migrate from one binding site at the OEC to another. Second, none of the channels permit unrestricted access of water to the OEC. The potential water channels currently proposed from a series of studies are the O1 channel, the Cl1 channel, and the O4 channel Fig.

The bottlenecks along each channel that may gate the entrance of the water molecules are shown in Fig. Recent advances in X-ray free-electron laser XFEL -based room temperature RT crystallography enabled us to study the dynamics of the structure of the water network under functional conditions 10 , 12 , 29 , The ability to take snapshots of the structure at the various time points at RT during the reaction allows for the investigation of water movements and changes in hydrogen-bonding networks in proteins These studies can provide new insights into the reaction mechanism in PS II by potentially identifying water and proton pathways.

They also provide starting models for MD simulations, using RT structures that are the catalytically relevant and functional states, along a reaction trajectory. In an earlier study by Ibrahim et al. In the present study, we focus on the question of mobility of the waters surrounding the OEC. We do that by combing the large dataset we have previously acquired throughout the Kok cycle to obtain a high-resolution structure at 1. Regions with more mobility will show a more disordered electron density, whereas regions of less mobility will be more distinct.

With this approach, we also identified more waters than previously within the channels described above. The presence of these waters in the high-resolution data enabled us to model them into the structure. Introducing these waters into the models for the S 2 to S 3 time point data and re-refining them led to improved electron density maps and the identification of additional waters. The S 2 to S 3 transition is a critical step as it is coupled with the first water binding to the Mn 4 CaO 5 cluster and the release of one proton.

In light of the newly provided information, we investigated the changes in the positions of the amino acid sidechains and the water network s that lead to the insertion of water into the open coordination site of Mn Mn1 10 , 11 , 12 , and the release of protons to identify the possible substrate intake and proton release pathway s in relation to previous computational and spectroscopic studies 8 , 9 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , We also investigated the structure of the water channels and the hydrogen-bonding network through a comparison of the cryogenic and RT crystallographic studies obtained using an XFEL.

A high-resolution dataset was generated by merging more than one hundred thousand high-quality diffraction images collected at RT from PS II crystals in various illumination states and a structure was refined to a resolution of 1.

In this high-resolution structure, the waters in the O1 channel have higher B-factor values than waters within the O4 and Cl1 channels Fig. Note that B-factors, or atomic displacement parameters, are directly proportional to the mean square displacement of atoms around their equilibrium position The waters with a high B-factor in the O1 channel are distributed through the entire channel, starting from the bulk waters lumen side to the waters close to the OEC.

The different B-factor values in the channels could be due to the crystal contacts. To check for such potential effects, we compared the B-factors of waters in both monomers, with fixed occupancy during the refinement, as they have different crystal contacts. We show in Supplementary Fig. See also Supplementary Table 4 and 5 for omit density peak heights and B-factors of waters in the individual datasets. The water molecules are represented using a color gradient scale, representing the B-factor of each water white color for B-factor 25 to red color for B-factor The water molecules detected within 3.

Extra water molecules in the 1. A comparison of the structural differences present in the O4 channel, O1 channel A and O1 channel B between the 1. Furthermore, several Fo-Fc difference density map peaks in the high-resolution dataset likely imply partial occupancy of highly mobile waters in the channels. In the O1 channel, the Fo-Fc peaks are distributed through the entire channel, starting from the bulk waters lumen side to the waters close to O1 of the OEC.

By contrast, the Fo-Fc peaks in the Cl1 and O4 channels appear only near the bulk water on the lumen side. The deviation of water positions from the S 2 -state was also investigated in these time point data Supplementary Fig.

However, the water networks are different in several locations between the RT and cryo structures. Small non-native molecules, i. These molecules are used as a cryoprotectant 21 , 42 , 43 , 44 , or as an additive during crystallization 10 , This implies that small molecules like cryoprotectants can pass through the cavity of the O1 channel. The presence of these molecules in the channel leads to changes in the water network due to their different hydrogen-bonding geometry.

Unlike the O1 channel, the waters in the much narrower O4 and Cl1 channels are less mobile, as discussed above and also shown by Ibrahim et al. A small difference in the cryo and RT structures is observed in the O4 channel, where four waters W are connected with charged residues and located right before the bottleneck formed by the residues D1-N, D2-N, and CPP, -L Fig. Hence, D1-N is the only connection between the penta-cluster waters W via W29 and a chain of waters W on the other side of D1-N, which in turn are connected to a hydrogen-bonding network to the lumen.

Extra waters, which are well identified in the combined high-resolution data and also present in the difference density maps Fo-Fc of the individual datasets, are included in the models of these time points.

Structural refinement, allowing water occupancy changes, results in improving the electron density maps and identifying new features.

Figures 3 , 4, and 5 show the structural changes in the channels O1, O4, and Cl1 at various time points during the S 2 to S 3 transition. O1 channel is in red. Each model overlaid with the model of the earlier time point, shown in a transparent color.

The waters are colored based on their occupancies, represented by a color gradient from white to red as shown at the bottom left.

The H-bond length is color-coded, as described at the bottom left. Source data are provided as a Source Data file. Appearance and disappearance of W, W, W, W, and W at different time points are marked with a red dashed circle.

The H-bonds are shown in dashed black line and up to 3. The mobility of waters in the O1 channel is higher than those in the Cl1 or O4 channels as shown above Fig. Prior to the insertion of Ox, the D1-E sidechain, which is ligated to Mn1 and Ca in the S 2 -state, moves away from Ca in the S 3 -state 12 , and Ox becomes a new bridging oxygen between Ca and Mn1.

Ibrahim et al. W25 is additionally H-bonded to Yz and W3. This decrease and increase of the electron density at W27 and W39 coincide with the starting of the Ox density build-up at the open coordination site of Mn1. This density indicates a new water at this position W Fig.

S 3 , its electron density drops significantly. It then extends further to the lumen side through the PsbO and PsbU subunits. The RT structural data reported earlier by Young et al. The same observation was reported by Kern et al. W20 named as W This disappearance is due to either W20 moving away from its position in the channel or having an increased mobility after the 1 st flash.

In both scenarios, the hydrogen-bonding network along the O4 channel becomes disconnected from the OEC in the S 2 -state and is restored only in the S 0 -state. As the changes in this area are also related to the changes in the Cl1 channel, we discuss them together in the next section.

Through D1-D61, the Cl1 channel is connected to W19, which is also the first water in the O4 channel. After the 1st flash, the Mn4-O D1-E distance is shortened from 2. The rotation of D1-E65 disturbs its hydrogen-bonding interaction 46 to D1-N 2. This also weakens the interaction between D1-E65 and D2-E 2. The rotation of D1-E65 alters the interaction to W 3. We note that this channel appears too narrow for water transport, but that transient openings occurring, at any studied time point, only in small fractions of the centers cannot be excluded.

This is accompanied by shortening of the distance between D1-E65 and D2-E from 2. However, the omit densities of W fluctuates during the S 2 to S 3 transition Fig.

Our study investigates the motion of waters and surrounding amino acid residues using snapshots of the RT crystal structures of PS II to identify substrate water and proton release channels. We focus on the S 2 to S 3 transition step, where one electron and one proton are released, and one water molecule comes into the OEC to the open coordination site of Mn1 as a bridging oxo or hydroxo ligand between Mn1 and Ca 10 , 11 , The water positions are largely preserved between the RT and cryogenic structures in the dark-adapted state, suggesting that most of the waters along the potential channels are highly structured, except at the exit of each channel into the bulk.

There are, however, some differences, which likely have important implications for the interpretation of the proton relay Fig. We have also observed sequential changes of several water positions at RT along the course of the S 2 to S 3 transition after the 2nd flash Supplementary Fig. Based on the above observations, we discuss the likely channels for proton release and water intake. For substrate intake pathways, the O1, O4 and Cl1 channels have been proposed based on theoretical studies 18 , 25 , 27 , 28 , 47 , 48 , Therefore, determining the substrate channel will help reducing possible substrate insertion pathways in the OEC that lead to Ox in the S 3 state.

The combined 1. Previously these water densities were visible in the timepoint data but were not included in the model due to the uncertainty 11 , In addition, the high-resolution data shows several Fo-Fc peaks Fig.

This is most likely due to waters occupying different positions at different time points or the presence of new partially occupied waters included in the combined data, implying more mobile waters in the O1 channel Fig. Besides, the combined high-resolution structure shows that the waters in the O1 channel have significantly higher B-factors than those in the Cl1 channel or O4 channel Fig. Moreover, in the crystal structures with glycerol or DMSO present in the crystallization process 10 , 24 , 42 , 44 , these molecules were visible in the O1 channel, but not in the Cl1 or O4 channel.

We hypothesize that such a decrease may be caused by the slightly altered water network in the O1 channel in the presence of small additives that influence the access or mobility of waters. We, however, note that the effect of such small additives in the O1 channel is minor and does not block the water oxidation reaction.

However, we cannot determine whether branch A, or B, or both serve as a pathway. Regarding the possibility of the Cl1 channel being the water intake pathway, we think this is unlikely due to the following observations: First, the mobility of waters in the channel is lower than that of the O1 channel.

Second, no structural changes were observed along branch B. Third, the structural changes observed at the bottleneck region in branch A do not allow a water to pass through. We think that the reversible motion of D1-E65 and the presence of less mobile waters makes the Cl1 channel more suitable to serve as a proton pathway Fig.

The opening of the gate by the rotation of D1-E65 could be caused by the protonation of D1-D61 and the subsequent rearrangement of the H-bonding network. We hypothesized that the proton released towards the bulk was shared between the D1-E65 and D2-E before. The deprotonated D1-E65 can then be stabilized by approaching D1-R Rotation of D1-E65 back to the original position and closing of the gate may be caused by proton transfer from D1-D61 to D1-E65 and the subsequent repulsion and attraction of the newly arrived proton by D1-R and D2-E, respectively.

Building upon the hypothesis of the O1 channel being the water intake pathway, we explore the question of how the water in the O1 channel ends at the open coordination site of Mn1 as a bridging ligand, Ox oxo or hydroxo , to Mn1 and Ca during the S 2 to S 3 transition 10 , 11 , A detailed description of the structural changes within this region was reported in Ibrahim et al. The main change is the tilting of the histidine side chain and the backbone, providing the driving force for the D1-E to move away from Ca While the motion of E, ligated to Mn1 and located close to the O1 channel, changes its position, there is not enough space for the direct insertion of water from the O1 channel to occur.

An alternative route for the Ox insertion is via W3, which is a ligand of Ca Ugur et al. If W3 is the entrance of substrate water to the Ox from the O1 channel, it likely needs to come via W4 first, which is refilled from the water wheel-like ring penta cluster of W26, 27, 28, 29, and 30 Fig.

In this case, Ca likely plays a pivotal role to shuffle water from W4, W3, and then to Ox. The gray arrow represents the possible proton pathway, while the blue dashed arrow represents the potential stepwise water insertion pathway.

This drop of the electron density is likely related to the loss or weakening of the H-bond to Yz due to Yz oxidation, thereby weakening the H-bond between W25 and the side chain of E, possibly priming it for replacing W3. The Cl1 and O4 channels as well as the Yz network, have been proposed in the literature as a proton release pathway 32 , 34 , 39 , 40 , 54 , 55 , The current structural study provides several indications of the Cl1 channel being the proton exit pathway in the S 2 to S 3 transition.

Below we discuss the possibility of proton transfer for all three pathways and provide support for the hypothesis of the Cl1 channel being the proton pathway in the S 2 to S 3 transition.

Theoretical studies suggested that the water chain in the O4 channel provides a downhill proton transfer 39 , In the S 1 to S 2 transition Fig. The dislodging of W20 disconnects the hydrogen-bonding network of the O4 channel from the OEC in the S 2 -state, and therefore it is unlikely that the O4 channel can serve as a proton release pathway during the S 2 to S 3 transition. This channel has been proposed as a proton release channel during the S 0 to S 1 transition 36 , 39 , 57 , In the RT structural data, however, one water W , which could be essential for proton transfer via this network Supplementary Fig.

Removal of this covalently linked fatty acid renders the fiber hydrophilic. Water absorption causes the hair shaft swelling. Excessive or repeated chemical treatment, grooming habits, and environmental exposure produce changes in hair texture and if extreme can result in hair breakage. Weathering is the progressive degeneration from the root to the tip of the hair. Normal weathering is due to daily grooming practices. When the hair is extremely weathered and chemically treated, there may be scaling of the cuticle layers, removal of the MEA and cuticle crack.

If the cuticle is removed, the exposure of the cortex and further cortex damage may lead to hair fiber fracture. The use of hair cosmetics may restore hair cuticle damage and prevent hair breakage by reducing friction and water pick up. Shampoos are not only scalp cleaners, but indubitably act as preventing the hair shaft damage.

Many scalp diseases are also treated by active ingredients that are added to the shampoo's formulations. It is desirable that whatever may the disease or condition be dermatitis, seborrhea, alopecia, psoriasis , the hair strands are kept aesthetically presentable, preserving its softness, combability and shine while treating the scalp. Shampoos are typically composed of 10—30 ingredients although products with as few as four ingredients are available.

The products are grouped into: 1 Cleansing agents; 2 additives that contribute to the stability and comfort of the product; 3 conditioning agents, intended to impart softness and gloss, to reduce flyaway and to enhance disentangling facility, and 4 special care ingredients, designated to treat specific problems, such as dandruff and greasy hair.

Conditions that are mostly affected by the use of aggressive shampoos are: Difficulty in untangling the strands, and the frizz effect. Attrition, the main cause of frizz, can be minimized by adequate formulation of cleaning products. On the other hand, if the shampoo formulas do not present the adequate composition, fiber attrition is aggravated.

Although considered as safe products, shampoos can cause contact dermatitis. Common allergens in shampoos are: Cocamidopropyl betaine, methylchloroisothiazolinone, formaldehyde-releasing preservatives, propylene glycol, Vitamin E tocopherol , parabens and benzophenones.

Surfactants are cleaning agents that substituted soap [ Table 1 ]. They act through the weakening of the physicochemical adherence forces that bind impurities and residues to the hair. Surfactants dissolve these impurities, preventing them from binding to the shaft or the scalp. The cleansing ability of a shampoo depends on how well it removes grease as well as the type and amount of surfactants used.

Residues are nonsoluble fats sebum that do not dissolve with water. In order to be removed from the hair shaft, surfactants present a hydrophobic molecular portion, and another hydrophilic.

The former will chemically bond with the fat, while the latter will bond with the water. The surfactants are generally composed of a chain of fatty hydrocarbons tail and a polar head. The polar extremity is capable of giving this portion of the molecule hydrophilic traits that allow it to dissolve in water and wash away the residues. The surfactants in contact with the water attain the structural formation of a micelle. Their structure becomes spherical with a hydrophilic exterior, which can be rinsed with water, and a hydrophobic interior where the fats and residues are binded.

When enough shampoo molecules have embedded their hydrocarbon ends in the particle, the surrounding water molecules attract the ionic ends of the surfactant. The particle then becomes emulsified, or suspended in water. In this form, it can be rinsed away. The main cleansing agents are anionic. The soap, which is also an anionic detergent, in contact with water, leaves an alkaline residue that is very harmful to the hair and skin and that precipitates in the form of calcium salts which accumulate in the hair strands, leaving them opaque and tangled.

Such effects do not happen with the new anionic surfactants that are derived from the sulfation of fatty acids and analogue polioxiethilenes alquil sulfates, alquil ether sulfates which are smooth cleansers and cosmetically superior. Theoretically the sulfatless shampoo creates a minimum electrical net, but there are no published analysis about effectiveness of these products regarding either cleansing power or hair shaft aggression.

Cationic, amphoteric and nonionic surfactants are added to some shampoo formulas to reduce the static electricity generating effects caused by the anionic surfactants.

Since they carry a positive charge, cationic surfactants bond quickly to the strands negatively charged due to the use of anionic surfactants and reduce the frizz effect. Besides, they optimize the formation of foam and the viscosity of the final product. The static electricity verified after the use of shampoo is exactly the result of a balancing out between the electric charges during the removal of sebum and residue.

Negative charge of the hair fiber repels the also negative charge of the micelle. The repulsion of charges allows rinsing with water. However, the result is an increase of the preexisting negativity of the strands and the formation of stable complexes that bond with the keratin, creating repulsion between the strands due to excessive static electricity. Although the cationic agents try to neutralize this effect, there is the interference of the shampoo pH, which can increase the static electricity and reduce charge neutralization.

Anionic surfactants are characterized by a negatively-charged hydrophilic polar group. Examples of anionic surfactants are ammonium lauryl sulfate, sodium laureth sulfate, sodium lauryl sarcosinate, sodium myreth sulfate, sodium pareth sulfate, sodium stearte, sodium lauryl sulfate, alpha-olefin sulfonate, ammonium laureth sulfate.

Although very good in removing sebum and dirt, anionic surfactants are strong cleaners and may cause an increase on electrical negative charges on the hair surface and increase frizz and friction. In order to minimize damage, other surfactants called secondary surfactants such as nonionic and amphoteric surfactants are added to the formulation.

Cationic surfactants have a positively charged hydrophilic end. Typical examples are trimethylalkylammonium chlorides, and the chlorides or bromides of benzalkonium and alkylpyridinium ions. All are examples of quats, so named because they all contain a quaternary ammonium ion. They tend to neutralize the negatively charged net of the hair surface and minimize frizz. They are often used as shampoo's softeners.

For the amphoteric surfactants, the charge of the hydrophilic part is controlled by the pH of the solution. This means that they can act as anionic surfactant in an alkalic solution or as a cationic surfactant in an acidic solution. They are very mild and have excellent dermatological properties. There are two types of amphoteric compounds: Alkyl iminopropionates and amido betaines.

Nonionic surfactants have no electric charge. They do not ionize in aqueous solutions because their hydrophilic group is of a nondissociable. Many long chain alcohols exhibit some surfactant properties. Prominent among these are the fatty alcohols, cetyl alcohol, stearyl alcohol, and cetostearyl alcohol consisting predominantly of cetyl and stearyl alcohols , and oleyl alcohol. Conditioners are used to decrease friction, detangle the hair, minimize frizz and improve combability.

Conditioners act by neutralizing the electrical negative charge of the hair fiber by adding positive charges and by lubricating the cuticle that reduces fiber hydrophilicity. They contain anti-static and lubricating substances that are divided into 5 main groups: Polymers, oils, waxes, hydrolyzed aminoacids and cationic molecules. Depending on the capacity of entering the fiber, the conditioner may reach the cuticle surface or the inner part of the cortex. Smaller molecules can reach the cortex.

Larger ones act on the cuticle. Bigger molecules The preferred route is intercellular diffusion or diffusion through the nonkeratin regions, although intracellular diffusion may also occur. They can be so substantive to the hair that they can be difficult to remove.

They are highly substantive to hair because of the hair's low isoelectric point pH - 3. Any cosmetic with higher pH bears a net negative charge on the hair surface, and therefore cationic charges positive are attracted to it.

The good correlation between silicone oil droplets stability, deposition on hair and resultant friction of hair support that droplet size and uniformity are important factors for controlling the stability and deposition property of emulsion based products such as shampoo and conditioner.

It is common to use cationic ingredients in many shampoos' formulations with anionic surfactants in order to result in charge neutralization forming a cationic-anionic complex, a neutral hydrophobic ingredient. Therefore, we can understand that the interaction between the ingredients is more important than the ingredient alone, as we are led to believe by the media.

It is very common to think that a new release product that contains a certain ingredient has the magic ability to transform dull hair into shiny and smooth hair. Most of the time, the major ingredients do not change, and sometimes the capacity of the ingredients to interact inside the shampoo's or conditioner's chassis or system is what makes the product acts better.

Bleached and chemical treated hair have a higher affinity to conditioning ingredients because they have a low isoelectric point higher concentration of negative sites and are more porous than virgin hair. Functions of the conditioners are:[ 5 , 12 ]. Silicones are hybrid inorganic-organic inert, heat-resistant and rubber-like polymers derived from cristal quartz.

Silica silicon dioxide common in sandstone, beach sand, and similar natural materials, is the initial material from which silicones are produced. Dimethicone is the most widely used silicone in hair care industry, and entropy is important for its adsorption to the hair surface.

Dimethicone is the main ingredient of the two-in-one shampoos. Others are: Aminosilicones, siloxysilicates, anionic silicones and others. They differ on deposition and solubility in a water medium, therefore acting differently on the hair. Some silicones can even enhance the shine of hair fiber by reflecting the light.

Dimethicone has the effect of protecting the hair shaft from abrasive actions while siloxysilicates increase hair body.

Polysiloxane polymers may re-cement lifted cuticle scales and prevent damage from heat. Amino functional silicones are cationic substances but not necessarily are more substantive to the hair than dimethicone, depending on the size of the molecule and the charge of the system. Dimethicones are hydrophobic, so they adsorb better on virgin hair and root rather than tips.

To enhance the deposition of dimethicone on chemical treated and damaged hair the products use cationic bridging agents which act increasing affinity between hair and the silicone.

Other polymers are the polypeptides and proteins for they are very substantive to the hair for having many ionic and polar sites for bonding and are large molecules to attach to the hair surface van der Walls force.

Protein hydrolysates, in particular those with low molecular weight distribution, have been known to protect hair against chemical and environmental damage. Many types of protein hydrolysates from plants and animals have been used in hair and personal care such as keratin hydrolysates obtained from nails, horns and wool.

Most of these hydrolysates are obtained by chemical hydrolysis and hydrothermal methods, but recently hydrolyzed hair keratin, feather keratin peptides have been obtained by enzymatic hydrolysis using Bacillus spp in submerged fermentation.

The hydrolysed protein derived from feather was deposited on the cuticle scales, and helped sealing the cuticle especially after heating with a flat iron, improving hair color and shine.

As the hydrolyzed aminoacids are positively charged, it is possible that the negative charge of the damaged hair attracts the positively charged molecules neutralizing the electrical charges and diminishing frizz and friction.

Keratin hydrolysates are usually prepared from keratin-containing animal parts, such as feathers, horns, hoofs, hair and wool, collected from discarded materials. Some industries have developed products that use a complex of nonanimal free amino acids derived from wheat, corn and soy proteins to mimic the natural composition of keratin. However, keratin is an irreplaceable protein in respect to its mechanical and protective properties, and the using of aminoacids do not replace or restore the damaged molecule structure.

There are few articles published about the effect of mineral and vegetable oils on human hair. The main physical property of this class of ingredients is the hydrophobicity of the oil.

Saturated and monosaturated oils diffuse into the hair much better than polyunsaturated oils. Oils play an important role in protecting hair from damage. Some oils can penetrate the hair and reduce the amount of water absorbed in the hair, leading to a lowering of swelling. The oil can fill the gap between the cuticle cells and prevent the penetration of the aggressive substances such as surfactants into the follicle.

Applying oil on a regular basis can enhance lubrication of the shaft and help prevent hair breakage. Rele and Mohile in , studied the properties of mineral oil, coconut oil and sunflower oil on hair. Both sunflower and mineral oils do not help in reducing the protein loss from hair. This difference in results could arise from the composition of each of these oils. Coconut oil, being a triglyceride of lauric acid principal fatty acid , has a high affinity for hair proteins and because of its low molecular weight and straight linear chain, is able to penetrate inside the hair shaft.

Mineral oil, a hydrocarbon, does not penetrate. Sunflower oil is a triglyceride of linoleic acid with a bulky structure and double bonds and has limited penetration to the fiber, not reaching the cortex. The mineral oil and the sunflower oil may have a film effect and adsorb to the surface of the cuticle enhancing shine and diminishing friction and for these, avoid hair damage.

Keis et al. Although thick films of oil can mask the lifted scales of the cuticle, it may leave an oily and heavy look to the hair. It is preferred to reapply oils that leave a thin layer on the surface and are well absorbed by the fiber.

In , the Brazilian oils and butters were studied by Fregonesi et al. Oil treatment reduced the combing force percentage for wet conditions. However, the hair treated with butters showed poor combing. Treatments using oils reduced the formation of split ends in the hair. Tresses treated with Brazilian nut and mineral oils gave the lowest formation of split ends. The reduction of combing forces is a combination of water wetting and the lubricant effects of the oil on the fibers.

Butters increased the combing force. Butters in raw state are not as fluid as oils and do not spread easily along hair tresses. The Brazilian nut, passion fruit seed, palm olein, buriti and mineral oils produced combing force reduction. Mineral oil has no affinity to hair's proteins and is not able to diffuse in the fiber.

Mineral oil main effects are its higher spreading capability on the hair surface which improves gloss, combing facility and reduces split end formation.

In Keis et al. Although coconut oil penetrates, the fiber and mineral oil does not, there is the equivalent reduction on water sorption for both oils. Increasing the thickness of the oil layer on the fiber surface increased hair moisture regain.

The oil that remains in the cuticle layer and not the oil that penetrates the cortex is the one responsible for the decrease in the water pick up. Marrocan argan oil has become very popular as a hair cosmetic main ingredient, referred as capable of keeping the hair moisturized and hydrophobic. Morocco's argan oil is now the most expensive edible oil in the world. The argan tree Argania spinosa L. Skeels , an endemic tree in Morocco, is the most remarkable species in North Africa, due to its botanical and bioecologic interest as well as its social value.

The oil is rich in tocopherols and polyphenols, powerful antioxidants. The fruit drying time influences the quality of the extracted oil. There are two main ways for a substance to penetrate the hair fiber: Transcellular and intercellular diffusion, transcellular diffusion envolves epicuticle, A-layer, exocuticle, endocuticle and is much harder path way because of the high cross-linked regions.

Intercellular diffusion envolves the intercellular cement, and it is the preferred route for large molecules because the low-sulfur and nonkeratin proteins are more easily swollen. Hoque BA. Handwashing practices and challenges in Bangladesh. A comparison of hand washing techniques to remove Escherichia coli and caliciviruses under natural or artificial fingernails. Composition and density of microflora in the subungual space of the hand.

Part 9. Washing and drying of hands to reduce microbial contamination. Field trial of a low cost method to evaluate hand cleanliness. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions.

Quantifying the effect of hand wash duration, soap use, ground beef debris, and drying methods on the removal of Enterobacter aerogenes on hands external icon. J Food Prot. Residual moisture determines the level of touch-contact-associated bacterial transfer following hand washing. Effects of 4 hand-drying methods for removing bacteria from washed hands: a randomized trial.

The hygienic efficacy of different hand-drying methods: a review of the evidence. Hand Hygiene in Healthcare Settings. To receive email updates about this topic, enter your email address: Email Address. What's this? Links with this icon indicate that you are leaving the CDC website. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.

You will be subject to the destination website's privacy policy when you follow the link. CDC is not responsible for Section compliance accessibility on other federal or private website. Preventing Occupational Exposure to Legionella Ensure your water heater is properly maintained and the temperature is correctly set. Determine if your manufacturer recommends draining the water heater after a prolonged period of disuse. Higher temperatures can further reduce the risk of Legionella growth, but ensure that you take measures to prevent scalding.

Flush your water system Flush hot and cold water through all points of use e. The purpose of building flushing is to replace all water inside building piping with fresh water.

Flush until the hot water reaches its maximum temperature. Anti-scalding controls and devices may limit the maximum temperature at the point of use. Care should be taken to minimize splashing and aerosol generation during flushing. Other water-using devices, such as ice machines, may require additional cleaning steps in addition to flushing, such as discarding old ice.

Clean all decorative water features, such as fountains Be sure to follow any recommended manufacturer guidelines for cleaning. Ensure that decorative water features are free of visible slime or biofilm. After the water feature has been re-filled, measure disinfectant levels to ensure that the water is safe for use. All Legionella testing decisions should be made in consultation with facility water management program staff along with relevant public health authorities.

Guidance on start-up and shut-down procedures from the Cooling Technology Institute CT external icon Ensure that the tower and basin are free of visible slime, debris, and biofilm before use.

If the tower appears well-maintained, perform an online disinfection procedure. Maintain your water system Consider contacting your local water utility to learn about any recent disruptions in the water supply. This could include working with the local water utility to ensure that standard checkpoints near the building or at the meter to the building have recently been checked or request that disinfectant residual entering the building meets expected standards.

After your water system has returned to normal, ensure that the risk of Legionella growth is minimized by regularly checking water quality parameters such as temperature, pH, and disinfectant levels. Follow your water management program, document activities, and promptly intervene when unplanned program deviations arise. Building managers may consider continuous monitoring of indoor humidity using a digital hygrometer, ideally more than once daily, to minimize the need to access the building.

After a prolonged shutdown and before occupants return, buildings should be assessed for mold and excess moisture.