Turbidity suspension

Basis. The rotational mobility of a small ligand is relatively unrestricted in solution (anisotropy approaches 0). The mobility is restricted when the ligand binds to a large immobilized molecule such as the receptor. In a T-format fluorometer, the parallel and perpendicular components of the emission can be examined simultaneously. While precautions must be exercised in working with turbid suspensions, it is nonetheless practical to make continuous measurements of binding and dissociation. 

Without polymer all absorbances increase with decreasing pH and with increasing salt concentration. This behaviour can be explained by the increased aggregation of the particles at low pH and at high salt concentration leading to a more turbid suspension. 

A suspension of tetraphenylphosphonium iodide (2.0 g, 0.0043 mol) in anhydrous ether (5 ml) was combined with a 1 N solution of phenyl lithium (5 ml, 0.005 mol). The reaction mixture was allowed to stand for 8 days, after which the dark red supernatant solution was decanted. (In addition to the lithium salts, it still contained 10% phenyl lithium.) The residue was washed with anhydrous ether under nitrogen. Thereby was precipitated the pentaphe-nylphosphorane as crude crystals. The supernatant turbid suspension was discarded. This purification procedure was repeated until the supernatant ether remained clear. The thus isolated product was recrystallized from cyclohexane under nitrogen to yield the pure pentaphenylphosphorane (1.79 g, 60%) of melting point (mp) 124°C. 

The principles of absorptiometry have been applied to the measurement of turbidity. Suspensions of particles scatter incident radiation and, while there is no absorption of radiation by the analyte, the reduction in the transmitted radiation can be used as a measure of the degree of turbidity. Because absorption is not involved, there is no requirement for monochrornation but the fact that the extent of light scattering increases as the wavelength of the incident radiation decreases explains the fact that some instruments do incorporate a simple monochrornation system. 

Estabrook, R.W., Peterson, J., Baron, J. and Hildebrandt, A. G. The spectrophotometric measurement of turbid suspensions of cytochromes associated with drug metabolism. In "Methods in Pharmacology". Chignell, C. F. (Ed.). 2 303-350. Meredith Corporation. New York. 1972. 

The short-acting insulins are dispensed with the insulin molecules in solution, thereby enabling a rapid onset of action. The intermediate- and long-acting insulins are dispensed as turbid suspensions such that mobilization of the insulin molecule from the... 

The Parr turbidimeter is an extinction type instrument, which consists of a cylinder to contain the turbid suspension, a lamp filament of fixed intensity at the base, and an adjustable plunger through which visual observation is made. Measurement is made of the depth of turbid medium necessary to extinguish the image of the lamp filament Standard suspensions are used to prepare a calibration curve, which is a plot of depdi vj. concentration. 

Juice Cloud. Mechanical extraction of citrus fruits yields a turbid suspension of wall fragments and cellular organelles in a serum composed primarily of cell vacuolar fluids. In most citrus juice products, such a suspension of fragments and organelles is a desirable component, since it provides most of the characteristic color and flavor (28). Essence and peel oils suspended in juice contribute desirable citrus notes to flavor, and these oils are rapidly adsorbed by juice particulate material shortly after extraction (29). 

Particles can be broadly classified as either colloids or as macroparticulate powders. Colloids typically have dimensions smaller than 1000 A and are optically transparent, while dispersed powders are generally larger and form turbid suspensions. Neither colloidal dispersions nor powder suspensions are usually monodisperse, and to the extent that particle size can influence attainable surface charge and area, many such systems will typically reflect a distribution of properties as a function of preparation method. Recent advances in synthetic techniques for providing materials with reduced polydispersity are likely to allow for better characterization of these effects in the near future. 

Among the first applications of this type of experimental strategy were screenings for protease activity [45,46], Here, agar plates containing a turbid suspension of casein... 

This structure is the traditional target for a group of antibiotics which includes the penicillins (Chapter 10), but a little-noticed report which appeared in 1948 showed that low concentrations of disinfectant substances caused cell wall lysis such that a normally turbid suspension of bacteria became clear. It was thought that these low concentrations of disinfectant cause enzymes whose normal role is to synthesize the cell wall to reverse their role in some way and effect its disruption or lysis. 

Prior to the isoelectric point, stable turbid suspensions of positively charged colloidal particles were obtained, but in all instances only a very small portion of aluminum and of phosphates was found in the precipitate (Table I). These suspensions were stable for at least six months, during which time there was no noticeable increase in the amount of aluminum or phosphate precipitated. 

The chemical reactions which they bring about are numerous and diverse. With many species a few cells introduced into a liquid medium multiply to a uniform turbid suspension in which the growth can be studied quantitatively by microscopic observation in minute counting chambers, by turbidimetric methods and other means. 

Infrared spectroscopy can be used in turbid suspensions, such as membranes or with big proteins, but the methods for studying the spectrum are impaired by the difficult interpretation of the composite bands obtained from proteins. Thus, more powerful methods of spectral analysis are needed... 

Formazin polymer, developed in 1926, can be used for turbidimeter calibration, and is straightforward to prepare, control, and reproduce. Standard procedures for the production of a stock formazin turbidity suspension of 400 NTU are given in American Public Health Association. Other calibration materials can be used (e.g.. Fullers Earth or Hach Gelex fixed standards - metal oxide particles permanently and statically suspended in silica gel) and may provide suitable alternatives, especially given the health concerns voiced in some quarters over formazin use. 

If necessary, dilute the turbid suspension to slighdy hazy using additional sterile distilled water. 

Inoculate each tube with yeast to yield a slightly turbid suspension. Incubate at 25°C (77°F). Examine for gas formation at 2-3 days and again after 1 week. Gas formation (fermentation) is detected as a growing bubble inside the Durham vial. 

A 3-neck flask fitted with a pressure-equalizing addition ftmnel is filled with 50 mL of DMF and cooled to -20 °C. Concentrated sulfuric acid (2.70 mL, 4.97 g, 48.6 mmol) was added over 5 to 10 min at a rate that maintained a temperature between -15 and -20 °C. The flask containing ketol 2 is placed in an oil bath and heated to 95 °C. At approximately 70 °C internal temperature, an 18.8 mL aliquot of the sulfuric acid solution is added as one batch. The reaction mixture is heated for 3 h at 95 °C an additional batch of sulfuric acid solution (7.5 mL) was added after 1 h. After the reaction is judged complete by GLC, the solvent is removed at 0.3 mm pressure to give a brown oil. The residue is dissolved in 375 mL dichloromethane, washed with two portions of sodium chloride saturated 2.0 N aqueous sulfuric acid (190 mL each), two portions of sodium chloride saturated aqueous sodium bicarbonate solution (190 mL each) and finally one 190 mL portion of brine. Each aqueous wash is back extracted twice with the same 190 mL portion of dichloromethane. The combined organic extracts are dried over sodium sulfate, filtered and concentrated in vacuo to yield approximately 39 g of an oily, brown semisolid. The residue is taken up in 78 mL of ethyl acetate and directly loaded onto a silica gel column (78 g) after elution with 600 mL of ethyl acetate, the column fi-actions are concentrated to yield 37.2 to 38.8 g of a tan crystalline solid. The solid is further purified by bulb-to-bulb distillation (120-135 °C, 0.1 mm) and recrystallisation. The approximately 36 g of yellow cream solid are dissolved in refluxing ether (74 mL). After addition of hexanes (19 mL), the resulting turbid suspension is cooled to room temperature, seeded and then placed into a 17 C water ice bath for 30 min. The precipitate is collected on... 

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